When I first install Windows Vista on a computer one of the first things that I like to check is the 'Windows Experience Index' (WEI) score. This feature gives me a good idea of how well the computer will perform with the new operating system.
To understand the WEI score, you may want to read the following article from Microsoft. Here is an excerpt: "When presenting at a user group meeting last week, someone asked me if a low Windows Experience Index (WEI) score of 1 or 2 means that he should not use Windows Vista on that computer. The answer is 'not at all.'
One of my favorite capabilities of Windows Vista is that it scales itself to fit your computer to help give you the best possible performance. For example, if your computer doesn't have the graphics capability to effectively display the new Windows Aero visual effects, Windows Vista won't enable those effects on your computer."