Did you actually set up a raid? As you're talking, I don't think you know what that is so I will assume not. Just FYI, RAID is where you basically use 2 or more harddrives to act as one. There are other methods, but this is the most popular I do beleive...
As for it not working, I'd say check you're bios. THe only problems I had with my new SATA drive was getting it to RAID correctly. Windows setup found my 2 drives without much of a problem... I suspect you just don't have something set up correctly in the bios. Maybe the drive's not actually set up or something?
Usally you can tell the BIOS to auto detect the drive. Set it to this rather than the default AUTO setting. Ifind that usally works better and a bit faster...
Hope this helps