[Hard Drive] Help: Second HD Disappeared after Reboot

I just hard restarted my computer after a lockup when attempting to close down Windows 7, and now after multiple normal restarts, it seems my second HD (D:/) is not being recognized by Windows and therefore I am unable to access my data on it. My POST report in the BIOS shows the drive in the proper SATA slot as usual so I am curious if anyone here has an idea on potential software fixes to re-activate my drive. Or worst case scenario does it sound like the hardware for my drive just randomly decided to die and I've lost that data for good? The drive is about 4 years old but it has never given me problems before.

Windows 7 64bit
NVIDIA 790i ULTRA SLI Chipset Mobo
Powercooler Radeon 7950 Video Card
8 Gigs Corsair DDR3 2000 MHZ Memory
HD 1: 150 Gig 10,000RPM Western Digital Drive
HD 2: 300 Gig 7,200 Hitachi Drive (CRASHED?)