unless you have 2 harddisks, it's wasted money. RAID comes in three flavors (I may have mixed up numbers):
x type 1: one disk mirrors the other. I use that today, expensive but best possible backup. Since each disk on one channel, performance = one disk.
x type 2: disk load-balance, one sector goes to one, 2nd sector to the other (kind of). If disks use 2 channels, speed of roughly 2x what you get with single disk (kidn of, in reality it will be 1.2 or 1.3)
x type 3: 3 or more disks, you get 1 and 2 so if a disk dies, you can restore (you just plug a new disk in and it gets populated so whole thing is transparent, at least that's how the REAL RAIDs work [KT7 is poor man's stuff so I don't expect too much, this kind of software is hard to do right]).
I got type 1 to work pretty easily but again, if you have 1 disk only and don't bother with either of the above, just wasted money.
Don't bother with overclocking for the start (beside RAM to 133), just switch on all the high-perf options on and you'll be amazed. Getting my 950 TBird to 1Gig got me around zippo performance improvement ;-) Better make sure that you get a video card good nuff.