KRNL386.EXE error

I am running WIN98SE.

My computer has been running fine. Today when I came in to work I found that
it was trying to shut down but apparently stuck on the "Windows is shutting
down" screen. I think that someone on night shift tried to reboot the
computer.

I powered down the computer and rebooted it. This is where I recieved the
message:

"While initializing device shell:
Cannot find or load required file KRNL386.EXE

General failure reading drive C

Abort Retry Cancel"

I powered the computer down and rebooted it. It got stuck loading the
desktop. I could see my desktop but no icons or anything. Just the color of
the back ground.
I rebooted again and it loaded Windows just fine.

Any ideas as to why this happened and how do I stop it from happening again?