Microsoft has released a beta version of Windows 7 Upgrade Advisor. You can use it to check if your PC can run Windows 7 (if you are already running Windows Vista, you will probably have no problems upgrading to Windows 7).

From Microsoft Site

“The Windows 7 Upgrade Advisor Beta is a pre-release version and is available in U.S. English only. While we consider this a stable and high-quality beta, it’s not the finished product.”