oooooh i love answering that question
the best way would be to use readyboost
WHATS THAT?! you ask?
well let me tell you
its the one of the only smart and original things microsoft managed to put into vista.
in essence, its adding to your "ram" by using a flash drive. vista is usually slow becuase it stores your preferences, habits and most used programs in the ram, leaving only a little bit and slowing your computer down considerably(its called superfetch). to counter that, use ready bost so it stores your preferences and small tidbits(main tasks like running computer programs are done on your main ram, only small other stuff which will not affect the system in any way if theyre suddensly deleted or terminated, like indexing and preferences will be stored on the flash drive)
basically, you take a usb flash drive(1 gig or more is good) and when it detects the new hardware, it will give you a small popup asking you what to do.
it should have an option available saying "use this drive" (if it is readyboost compatible, get a good, new flash drive if it isnt)and then you have to select that and use the maximum storage for maximum effect.
it works to such a good degree that with my 1 gig of ram on xp vs the 1 gig ram on vista + 1 gig kingston datatraveler readyboost(vista takes a lot of ram anyways so it should be equal right?) makes xp seem sooooooooooo laggy. i mean, like a bad server on an mmo lag.
hope that helped Harsky