A common question which techies are being asked alot now days is “is my computer compatible with Windows Vista?” or “Will my computer run Vista?”.
Microsoft has recently released a tool called the “Windows Vista Upgrade Advisor.

The Windows Vista Upgrade Advisor is a small tool which scans your computer, reports any potential compatibility problems and recommends ways to fix them. You can download the Vista Upgrade Advisor for download here: (doesnt work on 64bit based machines currently)
http://www.microsoft.com/windowsvista/getready/upgradeadvisor/default.mspx

As it stands today most people have some sort of compatibility, expecially with drivers (such as soundcards and video cards) and applications Windows Vista is unfamiliar with.