BIOS corruption and/or loss of Keyboard - using an AUTOFLASH disk
IF you appear to get an initial finding of the peripherals EXCEPT the keyboard on POST AND it is not a bad keyboard or related to the OS, you might try to refresh the BIOS with a BIOS flash for that motherboard. This would be accomplished with a floppy disk created to automatically boot and flash the motherboard. At this point it appears that this may be a potential fix as there have been findings related to successful use of this technique to reset corrupted BIOS due to electrical issues, spikes, etc..
An autoflash disk has only the basics [command.com, io.sys, etc.] and you create an autoexec.bat to *auto run* the commandline for the flash program. Make sure the autoexec and config sys contain nothing else, e.g., no drivers, no directions/paths, NOTHING except the command line necessary to flash the BIOS.
As you're having difficulty with the keyboard or the BIOS has been corrupted, you will need to make sure the boot block is also refreshed, and is included with the BIOS flash. Check on the MB site for the flash tool, its command line needs, AND the proper flash bin [or whatever it uses]. Most have a support forum so if necessary, ask there if the particular flash contains the boot block and was not indicated on the info for the download.
You need a system disk, NOT a recovery disk as that loads recovery tools, so make one or obtain one from some place like bootdisk.com
Once again, it is best to disconnect ALL other devices, leaving just the keyboard, video adapter, and floppy drive.
Make sure the autoexec.bat then contains the command to also refresh/overwrite the boot block as the defaults may NOT include this function, in addition to the standard updates that might be included within the BIOS update.. MAKE SURE that the computer you make this autoflash disk on is NOT configured to boot from the floppy to negate the potential of flashing the wrong computer with the wrong BIOS.
After creating the autoflash disk, make sure the target computer IS configured to boot from the floppy and has been reset to defaults [which it will be if you removed the battery], then run the autoflash disk.
NOTE: Another suggested command line addition is to save the old BIOS prior to the flash in case of continued issues as some sites will look at these files and attempt to diagnose any issues. Also, make a written note of what the present BIOS version and subversion is prior to the flash.
Again, if at all possible, remove the CMOS battery for about 10 minutes to completely remove any old settings [make sure no power is connected], re-insert after checking whether it is still good [generally 3+ volts] replace if needed [likely CR2032], and rebooting into the BIOS.
On the BIOS/CMOS standard setup screen, find Report All Errors or a similar setting, and set it to report none. Save the settings.
Reboot, watch the POST [power on self test] screen, then run the floppy flash disk. Remember to re-set any Bios settings if this appears to initially correct the issues, after re-connecting the devices. Power MUST be disconnected while doing so and grounding yourself first to discharge static electricity.