Making the assumption that the second hd is okay, and another assumption that you have them on the same ribbon cable attaching to Primary on the mobo, do the following:
Change the jumper to Master on your 1st hd, and Slave on the 2nd (occasionally "cable select" stops working). Make sure the 2nd hd is on the middle connector, and if there is a blue end, that goes into the mobo Primary. (An 80 conductor cable is much better than a 40.)
Reboot and go into BIOS. If your 2nd hd is there, Windows will find it.
Check all of this out and get back to us.