Computer won't recognize second WD internal HD

Question

Possible Duplicate:
Windows 7 won’t show SATA Hard Drive in My Computer

I installed a Western Digital Caviar Green 1TB internal hard drive, and want to use it for back up. My BIOS recognizes the device, but it is not recognized in Disk Management. It also is not recognized in "my computer." When I right-click my C drive>properties>hardware, I see it listed. First the drive was plugged into SATA port 1 on my motherboard, then I tried it in port 3, where it remains. I've been working on this for hours. Any help would be appreciated.

I should add that I looked up information for my motherboard and the hard drive in question, and it appears they are both SATA II compatible.

Motherboard: M2N78-LA violet6, manufactured by Pegatron. "Complies with SATA 1.0 and sata 2.0 specifications."

Hard drive:Western Digital WD10EADS-65M2B1. "Features the SATA I and SATA II interface."

More info

Hard drive model #:WD10EADS-65M2B1
Windows 7 Home Premium 64 bit Service Pack 1
Computer:HP Model p6404y