After reading your positive review, I downloaded Firefox 3.0, only to discover that some of my favorite add-ons, including a search toolbar, are incompatible. What can I do about this?

Wait. As I noted in the review, when major new versions of Firefox come out, it takes a while for some of the many add-ons for the browser to be updated so they are compatible with the new version. Because these are written by a very large number of different companies and individuals, the process will be gradual, and some will be updated more quickly than others.

As for search toolbars, like those from Google (GOOG) and Yahoo (YHOO), I doubt that most people still need them. When they first came out, these toolbars provided things the top browsers lacked: a permanent search box, pop-up blocking and a few other useful features. But all the major browsers now provide these things without requiring the installation of any external toolbar. The companies that make the toolbars can use them to sell advertising or attract you to their search engines. But, for many users today, they are redundant.

I don’t want to run antivirus software constantly, but I would like to periodically run a program that could scan my computer and remove viruses and the like. Does such a program exist?

Yes. Here’s one example. Microsoft (MSFT) makes a small, free program called the Malicious Software Removal Tool that looks for, and tries to remove, a limited number of the worst examples of malicious software. It can be downloaded at www.microsoft.com/security/malwareremove.

However, this isn’t a comprehensive antivirus program. Microsoft says it detects and removes only “specific, prevalent malicious software,” and advises that “You should also use up-to-date antivirus software to help protect your computer from other malicious software.”

I am in the market for a laptop. I was considering a Dell (DELL) or an H-P (HPQ) but have learned that Apples now run Windows. I have financial (Quicken) and other business files (Excel, Word and PowerPoint) that would need to be transferred to the new computer. Would this be possible on an Apple (AAPL)?

Yes, in the same ways you could transfer files from one Windows PC to another. For example, you could burn them to a CD or DVD, copy them to an external USB drive, or transfer them over a network or via the Internet. In fact, if you buy your Mac at an Apple retail store, the store’s staff will move your files over free, or for a modest fee, depending on which folders, and how many, you want transferred.

Once the files are on the Mac, you can either use native Mac programs to read and/or modify them, or you can install Windows and run your usual Windows programs to handle the files.

For instance, even if you never installed Windows on an Apple, your Excel, Word and PowerPoint files could be used in the Mac version of Microsoft Office. However, the Mac version of Quicken isn’t as compatible with the Windows version’s files. So, for Quicken, I suggest installing Windows on the Mac and running the Windows version of Quicken.

• You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital web site, http://walt.allthingsd.com.

Do Macs last longer than Windows PCs? I am willing to pay the additional cost for a Mac if it will last significantly longer, but if it has approximately the same lifespan as a PC from a reputable manufacturer, I will stay with PCs.

In my years of using both types of computers daily, I have never noticed a significant difference in when Macs and Windows PCs become unfit to use, and I have never seen claims from Apple (AAPL) that its computers last longer than competing models. Obviously, on the Windows side, there’s a much greater variety of manufacturers and of quality levels, while Apple makes all Macs, and receives generally high marks in well-known surveys of reliability. But so do some Windows PC makers. All computer makers turn out the occasional lemon, and how long a computer “lasts” depends tremendously on how you use it and how you judge its usefulness over time.

My laptop hard drive crashed last year and I lost some digital pictures that were on it. My daughter had accidentally copied those digital pictures onto her iPod but she didn’t select the option to store them at full resolution. I know I can get the pictures back off the iPod, but is there any software that can get them back at full resolution?

Not as far as I know. Unless you tell iTunes to store the photo at full resolution, what is on the iPod is a version of the photo that has been scaled down for the iPod’s screen resolution and storage capacity, and that is the resolution they would retain if you copied them back to a computer.

I have an H-P (HPQ) laptop using Windows XP and Microsoft (MSFT) Office 2003. If I purchase a new H-P laptop with Vista and Office 2007, what must be done to make the two machines compatible? My goal is to be able to take a copy of Office files from one computer and use them on the other.

The difference in the operating systems won’t affect your plan, but the difference in the Office versions might. The newer 2007 version of Office can easily handle your files from the older version. But Office 2003 can’t handle files in the new default Office formats introduced in the 2007 version. These formats use file suffixes that end in the letter x. For instance, the new Word format has an extension of docx, instead of the old, familiar doc.

Luckily, the new Office can still save files automatically in the old formats, if you change a setting. Here’s how.

On the computer with the new version of Office, click on the round “Office Button” at the top left of the 2007 versions of Word, Excel and PowerPoint. Then, in the window that appears, click on “Options.” In the next screen that comes up, click on “Save” in the column at the left. In the panel that appears at the right, you’ll notice an option called “Save Files in this format,” with a drop-down list of choices next to it. Display the list of choices by clicking on the arrow and select the format that corresponds to Office 2003. Then, click OK at the bottom of the window. For instance, in Word 2007, the format you want is called “Word 97-2003 Document (*.doc).”

The other option is to enable Office 2003 to handle the new formats, by downloading a free “Compatibility Pack” from the company’s “Download Center,” at www.microsoft.com/downloads. You’ll find it listed there under “Popular Downloads.”

• You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital web site, http://walt.allthingsd.com.

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about Microsoft Access and Macs, the toolbar in the new Internet Explorer and the latest version of Windows XP.

I have an old H-P notebook and am thinking of replacing it with a Mac. However, I use Microsoft Access to keep all the information of my clients and I was told by a friend that the Microsoft Office suite on a Mac doesn’t have MS Access. Is this true? If so, what do you suggest I should do? I mainly use Access and email.

Your friend is correct. Microsoft doesn’t make a Mac version of Access, and while there are some database programs for the Mac, there’s nothing I know of that’s exactly like Access or is fully and easily compatible with it. You could install Windows on your new Mac and boot into Windows when you need to run Access. In my tests of Apple’s Boot Camp software for running Windows on a Mac, Access ran quickly and well.

However, I suggest that you avoid the Mac and buy a Windows machine. If your main use of your computer is to run a single program that only works in Windows, that means that, even with a Mac, you’ll be spending most of your time in the Windows environment, and won’t gain many of the advantages of the Mac operating system and its tight integration with the Mac hardware. So, you might as well just buy another H-P or a Dell or Lenovo.

I was encouraged by your column of Oct. 19 to download Internet Explorer 7. It seems fine but I no longer have the Outlook Express icon on the toolbar. I found this quite convenient and wonder how to get it onto IE 7.

In the new Version 7 of Internet Explorer, Microsoft took pains to strip down and simplify the menus and toolbars, so as to streamline the look and feel. One of the things that was dropped as a default option was the icon for your email program, such as Outlook Express. But IE 7 allows you to restore it. Here’s how:

First, right-click on the toolbar, which is the short strip of icons that includes the Home button, and choose “Customize Command Bar.” Then, choose “Add or Remove Commands…”. From the list on the left, choose “Read Mail” and click the “Add” button. Then, with the “Read Mail” entry highlighted, use the buttons marked “Move Up” and “Move Down” to place the email icon where you want on the toolbar. Finally, click the “Close” button.

Several products you’ve reviewed recently, like Microsoft’s Internet Explorer 7 and Apple’s Boot Camp, require the “latest version” of Windows XP. What is the latest version?

The latest, and likely the last, version of Windows XP is called “SP2,” for “Service Pack 2.” The box will have that phrase on it. However, this version of Windows XP will be superseded in early 2007 by the all-new Windows Vista, which is a complete overhaul of Windows.

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Because of the volume of email I receive, I can’t routinely answer individual questions by email, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about using cellphones as modems for laptops, storing personal files from office computers and buying an ultralight laptop.

I would like to buy one of the new phones that run on high-speed networks from Verizon or Sprint and use it as a modem with my laptop. Do the phone carriers charge extra for this?

Yes, both Sprint and Verizon do impose an extra monthly charge for using this feature of phones like the new Treo 700p. They reason that if you access the Web on your phone, which has a limited browser and no hard disk to store large downloads, you aren’t likely to use a huge amount of network capacity. But once the phone is used as a modem with a laptop, it becomes very much like their laptop cards, for which they do charge a hefty monthly data fee. For instance, Sprint charges $40-$50 a month extra for unlimited data connections using the Treo 700p as a modem, depending on the length of your contract and whether you also have a Sprint voice plan.

I’m changing jobs after 10 years. What is the best way to take my personal files with me? I know Microsoft Office documents can be readily put on any storage media, but what about emails and contacts stored in Outlook? Can you offer some advice on how to best accomplish this move? (I am not taking any company property.)

Since this isn’t a legal column, I won’t weigh in on what constitutes personal data on a company computer. But it’s pretty easy to move your email and contacts from your Outlook to another copy of Outlook on a new PC at your home or your new office. In Outlook, go to the File menu. Select “Import and Export… “. Choose “Export to a File.” Then select “Personal Folder File (.pst).” Next, choose the Outlook folder containing the data you want to export. This could be your email Inbox, or any other email folder, or it could be the Contacts folder, or any other non-email folder, like Calendar. Finally, select the location where you want to save the exported data. If you are using a USB drive, use the “Browse” button to locate it. Then, hit “Next” and then “Finish.” Repeat the process for each folder you want to export. At the new computer, insert the drive with your exported data, launch Outlook, bring up “Import and Export…” again, and this time select “Import from another program or file.” Follow the steps to import a .pst file.

I am interested in purchasing an ultralight laptop computer for traveling, something I could carry in a messenger bag. I wish to use it mostly for Internet connectivity and word processing. I might even sneak in a DVD for use on the plane. I have looked at the Sony Vaio TX series and the Dell X-1. Are there others in the same size/weight category I should consider?

Yes. You might look at the HP Compaq nc2400 or the Lenovo ThinkPad X60 or the Gateway NX100X or the Toshiba Portégé R200. Except for the HP, none of these has an internal DVD drive, though, so depending on how important that is to you, you might have to spend more or go up to around four pounds. The Sony TX is excellent and combines low weight with an internal DVD. But it’s expensive. Other options for ultralights with internal DVD drives are offered by Fujitsu and Panasonic. I haven’t reviewed all of these, so I can’t recommend them all. My review of the Sony TX is at: http://ptech.wsj.com/archive/ptech-20051006.html. My review of the HP nc2400 is at: http://ptech.wsj.com/archive/ptech-20060518.html. My review of the ThinkPad X60 is at: http://ptech.wsj.com/archive/ptech-20060420.html.

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Because of the volume of email I receive, I can’t routinely answer individual questions by email, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about Apple’s new software, Boot Camp, that allows users to run Windows on a Mac.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

Now that Apple has made it easy to run Windows on a Mac, does this mean the opposite is possible? Can I also run the Macintosh operating system on a Dell or H-P or any other Windows machine? If not now, when?

No. Apple is happy to allow Windows on Macs because the company believes adding the Windows capability will sell more Macs. But it is opposed to allowing its OS X Tiger operating system to run on other companies’ computers, because it believes this will reduce Mac sales. Unlike Microsoft, Apple is in the computer business, not the business of selling the operating system by itself. It has rejected requests from other PC makers to license OS X, and has designed the Intel version of OS X to run only on Apple hardware.

Some hackers have claimed they got OS X running on Windows PCs, but not in any way that provides complete functionality or which is replicable by average, nontechie users.

If anyone does come up with an easy method, Apple is likely to alter OS X to defeat it. Of course, the company has changed course before, so anything is possible. But, for now, OS X works only on Apple hardware.

I know that with Apple’s Boot Camp, the Mac and Windows operating systems occupy their own distinct “partitions” on the machine’s hard disk. But can they view and use each other’s data files?

A: Yes, but it takes careful setup plus add-on software. Here’s how to do it.

When you run Boot Camp, you should make sure that the Windows partition you create on your hard disk is under 32 gigabytes. Then, when you install Windows, you should choose to format the Windows partition as “FAT32,” not “NTFS.” The FAT32 choice will allow your Mac to read and write to the Windows portion of the hard disk.

If you pick NTFS, the Mac will be able to read Windows files, but not write them. Note: You can’t choose FAT32 if the Windows segment of your hard disk exceeds 32 gigabytes.

After that, when you start up in Mac OS X, you’ll see the Windows drive and be able to access it from the Mac side. But, when you boot up in Windows, you won’t see, and can’t access, the Mac drive.

After the whole system is running fine, you should install a product called MacDrive on the Windows side. MacDrive, which costs $50 from a company called Mediafour, allows Windows PCs to access Mac disks.

The company says that MacDrive works on Boot Camp-equipped Macs. For more information, see: www.mediafour.com/bootcamp.

Will Boot Camp work on my iMac G5, or my PowerBook G4?

No, it works only on the very latest crop of Mac models, which began appearing this year, including the newest iMac and Mac Mini and the new MacBook Pro.

They are powered by Intel processors. If your Mac was bought before January 2006, or if its name includes the words G4, G5, iBook or PowerBook, it won’t work with Boot Camp.

Can I upgrade my older Mac to the Intel chips so I can run Windows on it?

No. Apple hasn’t made this kind of upgrade available. And, even if another company did, it would likely involve replacing most of the computer’s guts, not just one chip, and would likely cost almost as much as buying a new computer.

After I run Boot Camp, can I install my copy of Windows 2000? Can I use a copy of Windows I got with my Dell, or that I got from work?

No. Boot Camp works only with fresh copies of Windows XP, purchased at retail, that include the “SP2″ update from Microsoft in the box. It won’t work with upgrade versions of XP, or with copies that came with another PC, or that you got from friends or the office. And it won’t work with Windows 2000, or any other pre-XP version of Windows. You also can’t use Windows XP and then add the SP2 update later.