Will old software run on Windows Vista?

After my most recent blog post about XP and Vista, many users who are finally considering upgrading to the new OS have emailed me with the same question: Will my old software run on Vista, or will I have to upgrade all of that, too?

I've covered this issue a few times in the past, but the situation changes from month to month as new applications become compatible and other ones break. The bottom line is, yes, most software that ran on XP will run fine on Vista, with a few exceptions.

What won't run? Older security software designed for XP or earlier will almost universally not run; you shouldn't even try to install an antivirus or anti-spyware application on a Vista machine unless you know for sure that it is compatible with Vista. (It will say so on the box or when you download it.)

As for other older software, there's no way of knowing whether your program will run on Vista or not without simply trying to install it. Chances are it will work, but Microsoft never published a broad compatibility list for Vista, which has left millions of users guessing whether their software would work or not. However, when you first attempt to install an old app, Vista may pop up an ominous warning that the program you're installing is not compatible with the OS. Try to install it anyway: More often than not, I've had zero problems with the software after it was installed, despite Microsoft's warning to the contrary.

But even if the app won't run after installation, you still have another option for making it work: That's because Vista includes a system called Compatibility Mode, which lets Vista emulate an older Windows OS, all the way back to Windows 95. (XP actually has this feature, too, but very few people have ever had to use it.) If you install an app and it won't run, just right-click it, select Properties, and click the Compatibility tab. Check the box for "Run this program in compatibility mode for" and select another OS (typically Windows XP SP2) from the drop-down box. (See screenshot for example.) It ought to work most of the time, but again, be warned, do not use this trick for old security software.

If Compatibility Mode doesn't work and you can't find a Vista patch for the softwar online, well, you should probably upgrade.