This problem has already occurred a couple of times to me: after installing a fresh copy of Windows 7 onto the hard drive of my HP Pavilion laptop, the operating system boots up and loads to the desktop normally. After the first restart of the computer after the installation, the computer doesn't see the hard drive (500GB) anymore (not even in the BIOS). I'm completely baffled as to why this could be happening. Any help would be much appreciated!
EDIT: Just some more crazy info: while the computer does not see the hard drive in the BIOS, I press F2 at startup to go to the system diagnostics and the hard drive diagnostics run and PASS with no problem. It's really wierd.