A: Windows programs cannot be “converted” to run directly in the Mac operating system, which is called Snow Leopard. But, if you use virtualization software like Parallels or VMware fusion, and install Windows, then a Windows program like Microsoft Outlook can run simultaneously with your Mac programs. Technically, you are running it in Windows, but the two operating systems are active at the same time. With both of these virtualization products, you can even hide the entire Windows desktop, so that the Windows program you are running simply occupies a window on your Mac like any Mac program does. You don’t even notice that Windows is running.

In the case of files you created in Windows, the situation is even simpler. Most of the common types of files consumers use—including Microsoft Office documents, MP3 music files, MP4 video files, JPG picture files, text files, Adobe PDF files, and others—can be run in native Macintosh programs without conversion and without the need to run Windows programs. So you can just copy them to the Mac side and use them in Mac programs like iPhoto, iTunes, or the native Mac version of Microsoft Office, which uses the same file formats as the Windows version.

If you have an unusual or proprietary Windows file for which there isn’t an equivalent program on the Mac, you would run it in a Windows program, as described above.

If I am planning to upgrade a Windows XP machine to Windows 7, can I buy the upgrade copy of 7 or must I buy the full version?

A: According to Microsoft’s Web site, XP is one of the older versions of Windows upon which you can indeed indeed use the less expensive upgrade versions of Windows 7. The company’s online store says: “All editions of Windows XP and Windows Vista qualify you to upgrade. So, if you’re running either on your PC today, buy a package labeled ‘Upgrade’.”

I’ve been holding out (for what feels like forever) on purchasing a Netbook because I read that Apple was coming out with one. Can you tell me anything about when they might really begin selling them?

A: Apple executives have said repeatedly and emphatically that they don’t plan to offer a netbook, which is essentially a cheap, small laptop. Instead, Apple is widely believed to be working on a small slate or tablet device that would be controlled via a fingertip touch screen. This would be sort of like a larger iPhone or iPod Touch. The company hasn’t confirmed that such a product is in the works, but many analysts and Apple bloggers predict it will debut early next year.

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

I saw your recent review of ICE, the emergency medical information app for the iPhone. But my iPhone is set up to require a passcode to get to the home screen and run apps. Is there any way to display emergency contacts before a person enters the passcode?

There are some apps that allow you to customize the wallpaper of your iPhone or iPod Touch by adding a few lines of text that can be seen before it’s unlocked. One, called Close Call, displays a red cross and, next to it, an emergency phone number, and one brief line about, say, a key allergy or medical condition. The app is free, and is from a company called Polka, at polka.com.

I installed VMware Fusion on my Mac so I can run a virtual Windows XP computer on the Mac. When in the virtual Windows environment, I use security software. If I have the Fusion program shut down completely when I am not using it, will my computer be vulnerable to Windows security threats?

The vast majority of viruses, spyware and other malicious software is designed to run on Windows and cannot run natively on the Mac’s built-in operating system. So, while you are wise to use security software in your virtual Windows PC, any malware it misses won’t be able to run when Fusion is shut down. While even a virtual PC can get real viruses, this faux PC just disappears when Fusion is shut down, and so does all its software, including viruses.

But simply because Windows-based malware can’t run on the Mac’s OS, that doesn’t mean you don’t have to be careful. You can still be tricked by false email and Web sites into giving up personal information.

• 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.

I read your recent column about running Windows on a Mac. Is there a way to run the Mac OS X operating system on a PC, like a Dell or a Sony?

Yes, but it is really only for tinkerers and hackers, and even then, it may not work fully or smoothly. Apple makes the process difficult, both technically and legally, because, unlike Microsoft, it is not in the business of selling its operating system for use on other companies’ hardware.

Therefore, I know of no simple software for average consumers that can install OS X on a non-Apple computer without any technical knowledge and with full assurance that the operating system will be completely compatible with the hardware. There is nothing on the market like the products that allow people to run Windows on a Mac.

A small number of techies do install Mac OS X on non-Apple PCs every day, and some people have created software to make this possible for people with plenty of technical knowledge. There is even a company called Efix that is selling a hardware module that it says will make this easier. Its maker warns the product is only for “enthusiasts” and it requires that you attach it to the computer’s internal circuitry. Also, it only works with certain types of personal-computer hardware.

One more thing: Apple takes the position that its licensing terms limit the use of OS X to Apple hardware, so, even if you can pull it off technically, there could be legal jeopardy involved. In fact, Apple is suing a company called Psystar that sells non-Apple PCs with OS X pre-installed.

I have a new PC that came with a 64-bit version of the Windows operating system. It gives me a choice between using a 32-bit Internet Explorer or a 64-bit Internet Explorer. Which should I use?

The 64-bit version of Windows, which is rarely used by average consumers, can make the computer faster, but only when running programs that have been written in special 64-bit versions. In the consumer arena, there are too few such programs, and thus too little benefit, to justify paying extra for 64-bit machines. In fact, most people who have computers running 64-bit Windows are mostly using older 32-bit programs, which run fine, but aren’t made quicker.

So, the 64-bit version of Internet Explorer may run faster. But there is a downside. Because of the relative rarity of 64-bit users, some browser add-ons and toolbars and some of the Web technologies that power the features of Web pages, aren’t compatible with the 64-bit version of IE. On top of that, you may not notice any huge speed difference as the perceived speed of Web browsers depends more on the speed of your Internet connection than anything else. So, for now, I would stick with the 32-bit version, for compatibility’s sake. You can always install the 64-bit version later, if you decide that the Web sites you frequent and the add-ons you use work well with it.

I am running a Mac with Windows XP Pro in Boot Camp, which requires rebooting to change operating systems. Is there some way I can use my already-installed Boot Camp setup as a virtual machine using VMWare Fusion, so I can run my Windows and Mac programs side by side?

Yes, there are two ways. First, Fusion allows you to treat the Boot Camp section of your hard disk, called a “partition” — which is essentially a separate Windows PC stored on your Mac — as if it were a “virtual machine.” This approach still allows you to reboot the entire Mac into Windows when you’d like to do so, in order to perform the few tasks that Fusion can’t handle, such as advanced 3D graphics.

The second approach is to simply import the Boot Camp installation and turn it into a purely virtual Windows computer, as with any virtual Windows machine you would create in Fusion. If that meets your needs, you can then actually remove your original Boot Camp Windows installation, which will likely free up some hard disk space. To do this, just select your Boot Camp partition, which Fusion automatically detects, and click on Import under the File menu.

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

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

Do you know of a free or inexpensive program that will overwrite hard drives? My husband and I have updated to new computers, leaving us with two hard drives that have sensitive data that we would like to erase before disposing of them.

There’s a $20 program for Windows called Window Washer from Webroot that will wipe an entire hard disk so that its data is unrecoverable. Its maker calls this process “bleaching.” In cases where you don’t want to completely wipe a hard disk, the program can also securely erase individual files and folders, and can remove all traces of browser activity. I have tested it, and I can recommend it. You can get it at Webroot.com.

There are numerous other Windows file wipers, some of which may be free, though I haven’t tested them. To find these others, go to download.com and enter “file wiper” in the search box.

Since downloading the new Firefox browser, the panel at the top that shows the Web address and the back and forward buttons has disappeared. How do I get it back?

That panel is called the Navigation Bar and it can be turned on and off. It sounds like it somehow got turned off on your computer. To switch it on again, go to the “View” menu, select “Toolbars” and then click on “Navigation Bar.” The missing panel should reappear, and the next time you view that menu option, you will notice a check mark next to “Navigation Bar,” indicating it is on.

You can also use the same technique to switch the Bookmarks Toolbar on and off.

I have switched to Mac recently and never want to use Windows again. But the program I miss using on Windows the most is Microsoft Money. Do you know any way to make this program run on my Mac?

Microsoft (MSFT) doesn’t make a Mac version of Money.

However, all current Macs can run Windows and Windows programs. I suggest you pick up a copy of one of two programs — Parallels Desktop or VMWare Fusion. Both allow you to run Windows programs right alongside your Mac programs, even without displaying the Windows desktop. Microsoft Money would just appear in its own window, as if it were another Mac program.

This method works well, but it carries a price. Fusion and Parallels cost around $60-$70 each, plus you will have to buy and install a full, fresh, boxed copy of Windows.

• 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.