This meant I had to open it up. But before I could do that, I had to move my home computer out of the way, disconnecting it and setting it aside on the floor. Then I could open up the work computer.
The good news was that there was a diagram showing where to move the jumper to reset the BIOS to the initial state. The bad news was that I couldn't get at it. I spent about half an hour wrestling with it before I found a plastic cage that could be removed to get me access to the jumper.
Which I couldn't reach. Fortunately, daisy_knotwise had a foot-long pair of tweezers and I found an LED flashlight embedded in a fountain pen to provide the light to work with, so I was able to tease the jumper out. I restarted the machine which -- once again -- refused to POST, turned it off, unplugged it and put the jumper back.
Still no joy. Ok, let's start unplugging things. I unplugged the floppy. No help. I unplugged the DVD drive. No help. I plugged the SATA drive back in where it had been knocked loose. No help.
How about removing the battery, unplugging the machine, and then waiting for a while? Nope, that doesn't work either.
Mutter, mutter. The drive cage was supposed to pivot out of the way, but it wasn't budging. But here was a tab at the top of the case. Maybe that needed to be pressed too. I pressed it and pulled -- and out came the power switch and LEDs on a big piece of plastic. Oops.
Unplug everything from the back of the computer and try again.
Yay! Multiple POST error beeps. Let's plug the monitor and keyboard back in and reboot.
And the machine came up. This was very good. I checked the BIOS settings and declared victory -- and that no further tweaking would occur!
I started putting things back together. I put a new battery in as long as I had the case open.
And I found myself stymied by the plastic part with the power switch and LEDs on it. And that really had to go back in the case or the power switch wouldn't work.
Well, let's take off the top and other side of the case so I can get a better look. I remove the screws, but the case won't budge. There's a handle assembly on the top that has to be removed.
I grabbed my tablet and went to the Internet for a maintenance manual that explained how to take off the handle cover and then the handle itself. Finally, I got the top off.
This didn't really help, except it let me see what I was working against, so in the end, I was able to put the power switch back where it belonged.
I put the top and side of the case back on and put the handle back. Then I discovered that the case wasn't seated right, so that one edge was loose. So I removed the handle again, reseated the case, put the handle back on, and kept on muttering.
Reattach the floppy, reattach the DVD drive, make sure the SATA drive is connected, put the cover back on the case, and fire it up. Success!
Now, put the home machine back in position, wire it back up, and boot it -- also successfully.
I was really, really happy until I found the two big plastic parts from the work machine that I'd forgotten to put back in. But they aren't really necessary, so they're sitting in the closet waiting until the next time I need to open the work machine.
They can sit there for a long time.