My worst was when I flashed a BIOS. I religiously backed up the old BIOS to floppy. Then I flashed the BIOS. When I rebooted the computer it didn't find my hard drive. So I tried to reboot using the floppy disk containing the old bios, the computer didn't find the floppy drive.

I went nuts! I screamed and swore. The dog and cats hid in fear. I took a walk before I killed something. During the walk, I realized that the new BIOS had no idea what I had for peripherals and that I would have to enter setup to tell it. If anyone had seen me at the end of the walk, they would have had me committed.