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.

Best Buy is offering a free upgrade to Windows 7 if you purchase a machine today that has Vista. Is it better to wait to buy after the release of Windows 7?

A: I’d say so. If you buy a Vista machine now, you’ll likely have to spend at least some time and effort upgrading, and you may run into at least minor issues, which is something that sometimes happens even with straightforward upgrades. Since PCs preloaded with Windows 7 are only two weeks away, it’s worth the wait, unless you are in dire need of a new PC right away.

With the end of Microsoft Money, are there any good alternatives to Quicken? I tried Quicken Online, but it is just too limited.

A: I haven’t reviewed it, but a program called Moneydance might be worth checking out. It runs on Windows, Mac and Linux, and claims to import data from Money and Quicken. Moneydance costs $40, but there’s a free trial. Information and downloads are is at moneydance.com.

I read that upgrading to Windows 7 deactivates the license key for any prior version of Windows, ruling out any chance of reversing the upgrade if it doesn’t work out for some reason.Is this true? If I am going to take the plunge into Windows 7, I want to make sure I can always go back if I’m unhappy.

A: Microsoft says that’s false. The company emailed me to say: “The upgrade process does not deactivate the product key for the previous version of Windows. If you need to uninstall Windows 7 and go back to your previous version of Windows, you can activate it using the original product key.”

You can find Mossberg’s Mailbox and my other columns at http://walt.allthingsd.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.