I would just like to point out that the whole passage on why the Vista performance rating tool is an illogical is quite possibly the biggest load of rubbish I have read.
You claim that it “gives you a total score that can give you an indication whether or not your machine is fit for Vista”. No it doesn’t. If your machine in not fit enough to run Vista then it just simply will not run! 
“Anything higher than four is good as it means you can run Aero Glass really well”. Or so you claim. I only have a rating of 3.0 on my Vista Premium operating system and it runs Aero without any compromises. In fact, it runs “really well”. I have an Acer system at work with a 2.0 score and again, runs fine. 
The “Memory (RAM)” category is not done by the amount of memory you have but only by the memory operations per second. So doubling the amount you have will never give you a better score unless the speed is greater. And if you mess with the timings to give a reduced rate then the score will degrade. You can have 512MB of fast memory and still get a score of 4.2 (referring to my Acer machine at my place of work). I am running 2GB or Corsair Value RAM (£26) on my home unit and have a perfect 5.9, just to let you know!
This is my over all score and the breakdown:
Processor: Athlon 64 x2 400+ @ 2354Mhz score 4.9
Memory (RAM): Corsair Value 2GB score 5.9
Graphics: On-board GeForce6100 score 3.6
Gaming Graphics: On-board GeForce6100 score 3.0
Primary Hard disk: An old 160GB IDE unit from a 5yr old PC score 5.2.
The total price for the above self build is was only £152 excluding the OEM software. Just imagine my score with a modest £100 graphics card!