I saw your column last week saying Apple’s MobileMe now does a better job of syncing contacts, calendar items and email. But will it allow me to sync to my iPhone directly from my company’s corporate calendar, address books and email?

MobileMe is meant for consumer data, not corporate data. Essentially, Apple’s own servers act like a company’s servers in order to bring corporate-style push syncing to consumer data that isn’t kept on corporate servers. To sync your corporate contacts, calendar items and email to an iPhone, you would use a different built-in option in the iPhone: Microsoft Exchange. Assuming your company’s IT department certifies the iPhone as an acceptable device, and your company uses Exchange, as many or most do, you can use an iPhone to perform instant two-way syncing of corporate contacts, calendar and email. It works just like a BlackBerry or Windows Mobile phone in this scenario. I have tested this, and found it worked well.

Is it possible to sync a Treo or BlackBerry using MobileMe? If not, how can I transfer my Treo contacts and calendar items to the iPhone?

While MobileMe is agnostic when it comes to computer platforms, working on both Windows and Macintosh computers, it is single-minded when it comes to handheld devices. It synchronizes data only to Apple’s own iPhones and iPod Touch devices. It doesn’t work with the Treo, the BlackBerry, or any other smart phone or handheld device beyond those made by Apple. One simple way to move contacts and appointments from Treo to iPhone is to use Outlook as an intermediary. First, sync your Treo to Outlook. Then, just plug your iPhone into your PC, launch iTunes, and sync the iPhone with Outlook. The data from your Treo should then be on the iPhone. MobileMe isn’t required.

I can’t find the location of the files contained in my Personal folders in Outlook that contain my contacts and saved emails. Can you help?

To find the location of the single combined Outlook data file that contains your email, contacts and calendar, follow these steps. First, select “Data File Management” from the File menu. A window will open showing the name of your data file, which includes its location on your hard disk. Click the button to the right that says “Open Folder,” and you will be in the folder that contains this file, with the file’s name or icon highlighted. Outlook data files use the extension “pst” at the ends of their names.

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

Should I install Microsoft’s “SP3″ upgrade to Windows XP? I hear opinions on both sides.

In general, I recommend this upgrade, officially called Service Pack 3, because it beefs up security, and that helps not only you, but all Windows users, to avoid the spread of malicious software. If your PC is more secure, it is less likely to be used as a source from which other PCs can be infected.

I have upgraded a couple of XP PCs to SP3 without any downside. However, like you, I have also heard from some users that the upgrade caused them problems.

As with any major operating-system upgrade, either outcome can occur, depending upon your computer’s particular configuration and condition. So, if you’re on the fence, consider your level of concern about security.

How do cellular data cards compare with fast cable modems in terms of Internet speed? Are these cards more secure than Wi-Fi?

In my experience, using and testing cellular data cards on various laptops, they typically deliver, in real day-to-day use, somewhere between 300 kilobits per second and 1.5 megabits per second. By contrast, a fast cable Internet service can actually deliver up to 16 mbps. So cable is much faster.

Your security question is much more complicated. Wi-Fi security can range from very poor to quite good. It depends on where and how you use Wi-Fi, how you or others have set up the wireless network, and how you have configured your own computer.

Accessing the Internet over a cellular network is a more controlled process, because the cellphone-network operator manages the transmission, and in most cases supplies and configures the software on your computer. So, it is likely to be safer than the worst Wi-Fi setups. But I would never suggest that cellular data card transmissions are invulnerable to hackers or criminals.

What’s the difference between file-based backup and image-based backup software? Why would I choose one over the other?

Image-based backup software copies an image of your entire hard-disk, including all the programs, settings and obscure files that you never see. While it can be used to recover individual files, in some cases, it is mainly designed to allow you to restore your entire hard disk in the event that you lose it all.

File-based backup software, which is more common among consumers, is typically designed to preserve a copy of only your personal data, the material you can’t re-purchase or re-install if your hard disk dies.

That includes word-processing files, spreadsheets, presentations, emails, contacts, calendar items, photos and other items you created. It also is often used to back up music and video files that would be time-consuming, or very expensive, to re-acquire. And in some cases, it can preserve settings and preferences, such as Web bookmarks.

Both types of backup generally begin with a time-consuming initial session, followed by shorter sessions to update the backup with incremental changes.

Many people choose file-based backup because it occupies less space, and is generally quicker and also less expensive. Image-based backup is for folks who are willing to spend the added money and time to be sure they can restore their whole computer, or clone its contents completely to another machine.

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

When will Google offer its much-discussed cellphone for sale?

Google says it isn’t planning to build or sell mobile phones. Instead, it is developing a cellphone operating system, or software platform, called Android. And it has assembled an alliance of companies, including phone makers and cellular network providers, to create phones based on this new platform. This group is called the Open Handset Alliance. In addition, since Android will be so-called “open source” software, Google expects numerous developers around the world, large and small, to modify the operating system and create programs that will run on it.

If all goes according to plan, Google says it expects to see many different Android-based cellphones and other mobile devices, from a variety of manufacturers and carriers, in various designs and with differing functionality and capabilities. Some may be larger-screen “smart phones,” similar to an iPhone or BlackBerry. Others might be smaller, simpler phones. Still others might fall somewhere between an iPhone and a small laptop.

Google officials say they expect the first Android devices to be available later this year.

After reading your Jan. 3 column, I looked unsuccessfully for a Home and Student version of Office for Mac 2004. Does such a version exist?

In the 2004 release of Microsoft Office for the Mac, this low-priced version had a different name: the Student and Teacher edition. Microsoft presumably changed the name of this $150 product to the Home and Student edition in both Office 2007 for Windows and Office 2008 for the Mac, because, while it was technically limited for sale to families containing students or teachers, no proof was required and it was widely purchased by consumers in general.

However, there’s a big difference between the latest Windows and Mac versions of the Home and Student edition. In the Mac version, it includes Word, Excel, PowerPoint and Entourage, Microsoft’s equivalent of Outlook on the Mac, which, like Outlook, includes email, calendar and contact functions. But the new Windows version now omits Outlook, and instead substitutes OneNote, a note-taking and information organizing program that is far less commonly used. So, Windows users must spend much more money to get a version of Office that includes Word, Excel, PowerPoint and Outlook.

Is there a way to back up Microsoft Outlook Express emails, particularly Inbox items?

Outlook Express stores your emails in database files, with all the messages in each of your mail folders lumped into a single such file. These files can be backed up, or copied, onto other hard disks, or storage media.

The email data files are usually buried in obscure subfolders in Windows. But you can locate them by clicking on the Tools menu, then Options. This will open a tabbed window. In this window, click on the tab called Maintenance, then the button called Store Folder. This will generally give you a long, complicated path to the folder.

Next, copy this path by selecting it and pressing Control and C. Then, click on the Start menu, select “Run…”, and then press Control and V and then click OK. This should open the folder that contains your email. The inbox is contained in a file called Inbox.dbx. This is the file you will want to back up. If you want to back up other folders, such as the Sent mail folder, you will find them along with the inbox file, with the same “.dbx” suffix.

Some backup programs may automate this process by simply allowing you to designate that you want to back up your Outlook Express emails. There are even some programs specially designed to back up Outlook Express messages. You can find some of these by simply performing a Web search on “backup Outlook Express.”

• 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.