Due to a failing Samsung hard drive that shipped with my system, I decided to do a full upgrade on my system. I went to a 10000 RPM Western Digital (WD3000GLFS) drive for starters, then upgraded my system RAM from 3 Gigs (all that is really useful under 32x Windows) to 8 Gigs.
Even though I got the fastest RAM available (upgraded from 667 to 800), the Windows Experience program only boosted my RAM rating from 5.3 to 5.5 (everything else is 5.9).
Since there is a dearth of 64x applications, I have yet to see the system utilizing more than 3 Gigs of RAM at any time. So basically I have 5 Gigs of RAM sitting around being bored and wishing they were in a server.
I can say though that overall performance is much faster and crisper. Then again perhaps I am just imagining that to compensate for the $500 ($300 for the drive and $200 for the RAM) upgrade price.