Hd is PATA? Is it the one in your sig?
What brand is the HD.
Make sure you have the Slave/Master in order! Theres always the CableSelect position on some drive that can be usefull.
Anyhow sounds like a master/slave issue to me
Asus P4P800DX, P4C firstname.lastname@example.org, 2X512 OCZ PC4000 3-4-4-8, MSI 6800Ultra stock, 2X30gig Raid0