Question : Problem: XP and Vista not reporting 2 hard drives - bios sees them both

Hello
I have a Gigabyte GA-965P-DQ6 motherboard, with 2GB ram and two Samusung spinpoint P160 hard drives - one with XP installed, the other with Vista Home Premium installed. The graphics card is an MSI NX7900 GT/GTO (Nvidia GeForce 7900 GT/GTO) with 512MB ram.  
This week, Vista became unstable and crashed on various applications (explorer.exe, iexplorer.exe, while in control panel, while just sitting on the desktop).  Now neither Vista nor XP will reboot from a restart.  I have to switch off, and do a cold boot.  The bios sees two hard drives and using F12, I can select which disk to boot from.  However, once into the system, the computer management consol only reports one hard drive.  
I want to do a complete rebuild of the Vista disk and which to transfer all the data files to the other hard drive but obviously I can't do this.  Has anyone any ideas?  (I have tried system restore and I've also rolled back a recently installed Nvidia driver)
Thanks
Anne

Answer : Problem: XP and Vista not reporting 2 hard drives - bios sees them both

Let's see if that new drive makes a difference, if not then you'll know it's a good possibility it's the board.