F8 to bring up a menu with options like "Safe Mode" has nothing to do with the BIOS. It is part of the Windows Boot Loader (Bios starts, does it's bit then passes control to a boot loader which then loads the Operating System). In your case with "can't find operating system", I think it is failing to find this boot loader program, either because the hard disk is "missing" or (given your chain of events, I would suspect...) because the boot loader is missing or corrupted.

BIOS is more commonly entered by pressing F2 or the delete key (and again a message may come up to show you what to press). The one thing that you could look at in there is whether or not it is detecting the hard disk. If you try that, just escape or follow menus to quit the BIOS, do not change any settings.