Western Digital Raptor 36.7GB not recognised in ASUS P5AD2-E

I just bought 2 WD raptor 37.6Gb and want to set up a raid 0. however, when I plug the these two drives in the mobo and boot up into bios. it detected one of the WD 36.7 as a WD 400BB? how come?

hmm im not sure if this is a common thing but when i was putting together a friend's system it only would detect one raptor at a time, not 2. so he ended up getting an IDE drive and it works grea in conjunction with his raptor, in not sure why