If your PC already runs Windows Vista, it will probably run Windows 7. In fact, Windows 7 runs better on some PCs, mostly laptops, than Windows Vista does. If your PC already runs Windows XP well, it will probably run Windows 7, but perhaps not at its best. Upgrading your PC with a few things will help Windows 7 run better. This is what you would need to go in for: Video: Windows 7 requires powerful graphics for its fanciest 3-D features. But if you don't have ready cash to upgrade the video cards, don’t despair. Windows 7 simply slips into more casual clothes, letting your PC run without the 3-D views. Memory: Windows 7 loves memory. For best results, your PC should have 1GB of memory or more. Memory’s easy to install and relatively cheap, so don’t skimp here. DVD drive: Unlike Windows XP, which comes on a CD, Windows 7 (like Windows Vista) comes on a DVD. That means your PC needs a working DVD drive to install it. That probably won’t rule out many PCs these days, but it may rule out some older laptops and netbooks. Windows 7 can run nearly any program that runs on Windows Vista, and it can run a great number of Windows XP programs. Some older programs, however, won’t work, including most security-based programs, such as antivirus, firewall, and security programs. You’ll need to contact the program’s manufacturer to see whether it’ll give you a free upgrade.