Keyboard quit. ?Windows glitch or motherboard problem?

My keyboard quit working -- no response to any key. My
mouse continues and work and I can operate all of my
usual programs as long as I use the mouse. I tried my
husband's keyboard on my computer and it would not
function either. (My keyboard works just fine with his
computer -- so it must be something in either my computer
or my computer's programs.)

Three local computer repair shops have told me the same
thing: The keyboard 'shutdown' is probably a hardware
failure, probably the motherboard. (It is an eMachine -
about 5-6 years old - but everything in it has been
updated -- except the motherboard.)

One shop suggested it might be a Windows glitch -- and
that I could find a patch for this particular XP bug that
might 'fix' my dead keyboard. (I'm typing this on my
husband's computer.)

Can you tell me where to look to find a 'fix' for my
problem? I'm cringing at the idea of $200+ for a new
motherboard -- and $400-500 to replace the computer. Any
help will be greatly appreciated!
Thanks!
Linda