Had a desktop Dell Optiplex 330 be knocked over around 5 times a few weeks back and its driving me mad trying to fix it.
At first when trying to boot up, the computer would reach just past the F2/F12 screen for setup, but then error on a black screen asking for CTRL+ALT+DEL to reboot. This would just loop over & not boot correctly. The harddrive was put into a spare computer and files recovered onto a spare WD80GB HD.
The Dell doesn't have a CD-ROM drive in it, so i took the one from the spare HP computer, and plugged in as nessesary into the Dell, along with the faulty HD to re-format. I've set the Boot sequence to CD-ROM 1st. The Windows XP disc loads fine, up until "Starting up Windows" at the bottom bar, and then BSOD appears before any of the normal re-format/install can be done. It displays STOP:0x0000007B (0xF78E2524, 0xC0000034, 0x0000000, 0x0000000) I don'y know if that it much help. I have tried 2 separate WD harddiscs with this desktop and both produce the same problem. Could this possibly be a fault with the motherboard?
I'm not too clued up on PC's (Work with Firewalls mainly) So sorry if i seem a little uneducated!

Don't worry about being uneducated about computers. We all start out as novices. Your error is described as the following:

0x0000007B: INACCESSIBLE_BOOT_DEVICE

Windows lost access to the system partition or boot volume during the startup process. Typical causes: Installing incorrect device drivers when installing or upgrading storage adapter hardware, or a virus.

If i am reading this correctly I suggest re-posting in the General Hardware forum (or possibly the Storage forum because they deal with HDs there) because you've tried two different WD drives and yet you can't install.