One thing about the HDD FAQ:
RAID 1 = mirroring (Excellent for redundency, but does nothing for speed. Requires at least 2 drives)
RAID1 can improve read speeds significantly, but does nothing for write speed. And you'll definitely want to keep the two HDs in separate IDE channels. And "redundancy" spells reliability, at the cost of capacity. Two 80GB drives in RAID1 would only give you 80GB, with a built-in backup (both drives hold the same data).
If you haven't read e.g THG <A HREF="http://www6.tomshardware.com/storage/02q3/020830/index.html" target="_new">IDE Training Course, Part 3: Using RAID</A>, please do so.
<font color=green><i>Feet are frozen, hair's on fire, on the average, everything's fine.</i></font color=green>