Urgent boot problems!

Hey sorry for the urgentness, but i am being searious, it is urgent.
I had two hard disk drives in my pc, one on an IDE cable, the same cable used for the CD drive. The other sata2. They both had xp installed and when you booted up off the hdd on the ide it asked to select your operating system. I always chose the first one, which was the os on the sata2 drive. Now after deleting the partitions on the hdd on the ide cable and setting the first boot device to be the sata2 HDD, it fails to boot, it returns the error "insert proper boot device and reboot". Im really confused. This is my brother pc, all his things were on the sata2 hdd, and we never used the drive on the IDE cable, i thought it would be pretty simple just to whipe the data on the spare HDD, (using the xp installer disk to delete the partitions) but by doing so it has killed the other HDD. My brother doesen't know yet, and the windows xp installer disk is saying that space is taken up on the other HDD so his stuff is still on there i just can't boot off it. Mobo seems to say there is a device on the sata2 when it's starting up.

Any help at all would be greatly appreciated. Maybe reinstalling xp on the spare hd???