Re: sata speed
IDE : 133MBps for the latest drives (that's peak [fastest], not sustained)
SATA : 150MBps (again peak)
SATA 2 : 300MBps (and again, peak)
Basically, unless your PC is brand new it won't support SATA 2. The IDE to SATA at the moment is pointless, as your hard drive is only running at SATA speeds.
SATA is faster in sustained as well as peak. I bought a Seagate Barracuda 200GB 7200.7 and it's great. Make sure you get the 200GB, not the 160GB, as the 200GB has 2 100GB platters, and the 160GB 2 80GB platters. This means that the 200GB can find data faster!