I'm not sure what's going on, but it could be a hardware problem. Perhaps a cable came loose during moving. Or, it could be a worse hardware failure. Do you hear a beep when the system is booting?
If it were simply the motherboard battery going dead or something, that shouldn't stop the A: drive from working, I wouldn't think. You should still be able to boot up into DOS with the floppy. It's good that you can get into BIOS. At least something's working.
While you're in the BIOS, does it show the hard disk at all? Does it show the floppy installed? Have you tried the boot disk on another computer to see if it works? And when you say, "Nothing seems to make a difference," do you mean that you get the "invalid system disk" message when you try to boot with the floppy? (Just covering all the bases.)
Edited to add:
There is also the possibility that you have a CMOS virus that is preventing disks from working. Hint: ALWAYS write-protect your startup floppy disk!
If you do have such a virus, it can write itself to the floppy, and then infect another machine. If you used it and did not write-protect it, discard it and make a new one, then write-protect it before you use it.
Edited by Herk, 29 May 2005 - 04:26 PM.