Microsoft has the answer: the Windows 7 Compatibility Center on the Web. This has a complete list of compatible hardware and software that is supported in Windows 7. So if you have questions about compatibility with things you already own will work with Windows 7 this site is for you..

http://www.microsoft.com/windows/compatibility/windows-7/en-us/default.aspx

If you are still of Vista there is a compatibility center there as well..

http://www.microsoft.com/windows/compatibility/windows-vista/