Hardware

could you have unplugged or partially unplugged some things? I would open it up and take a look.

Have two thoughts on this that might be helpful.

First, check your BIOS settings to see if a 'Quick Power On Self Test' (or something similar) is enabled. If so, disable it so POST can recheck all system parameters and possibly update the checksum. My best guess here is that the expected configuration checksum stored in BIOS disagrees with what was encountered during the quick power on test because a new device was installed. You can always re-enable this setting after the configuration checksum has been reestablished.

The floppy error is the one that baffles me. This could be part of the inequality in the checksum check. From what I remember, part of POST was to see if a 40 or 80 track floppy was installed. Check to see if BIOS has a 'Boot-up Floppy Seek" (or something similar) setting. If so, disable it and see what happens. Just like some compilers sometimes point you to the wrong line of code for an encountered error, I wonder if it's possible that this particular BIOS/POST isn't doing the same.

Please let us know what happens in any case.