Actually it worked waaay back on NT4.0 and Win98! I used to teach students that trick in A+ PC repair classes I taught.
Everytime I used to do it back then, clients would call me or email me on "How much faster their PC was", and all I did was defrag, disk cleanup, etc, and a few registry tweaks.
This is still one of the best "secrets" out there, but todays HW is so much faster I doubt it is needed like back in the day!
