Sounds bad. Looks like you may have to find another PC to copy the data off the hard drive. I don't know how standard the case for that is but you may be able to get a second hand 486 board from a place like http://www.hitechcafe.com/
I'm trying to think of what I've done to resurrect near dead machines before... maybe another keyboard? I've had bad keyboards wreak havok with systems. It could be the power supply, have you got another one you can try? There's also the old pencil eraser trick - use an eraser to clean the contacts on all your cards, especially the video and IDE cards. Actually, try that first. I've had it work wonders for me in the past.