CNET has the answer. Actually, it has 3 answers, depending on whether
you are a Basic Home User, a Mainstream User or an Enthusiast.
The test seems comprehensive, but doesn't take very long. I'm guessing
it was less than 5 minutes. When the testing is done, you are provided with 3
lists detailing their recommended upgrades to get your computer ready for Vista.
Each list is tailored to the type of user, Basic, Mainstream or Enthusiast.
Here is the link:
http://help.cnet.com/9602-12576_39-0.html?messageID=2509166&tag=tip-2509166