Jerky mouse movement

I've got a Celeron 400 system that I overclocked for a couple of years at 450. It always ran fine. About 3 or 4 months ago I began to get hesitation in mouse movement, particularly in Netscape 4.x and in MS Word 97. It was like while the processor worked on one thing the mouse had to wait for its movement information to be processed.

My first guess was the dual fans and they had been squeeking so I replaced them both thinking maybe the processor had been overheating. This was good probably for the processor but didn't help the mouse problem.

Next I figured I simply had cooked the Celeron after a couple of years of overclocking. I bought a C433 and stuck it in. That too did not solve the problem.

So, what might give here. Perhaps a Win98SE problem? Memory? Motherboard? Also, the clock won't keep time any more...loses 10 minutes in a couple hours and then works fine for days.

Oh, and as I can see from typing this the keyboard occasionally will do a half second or so lag from key struck to cursor movement.

The computer has been around a few years and I'm not sure of the specific components anymore but could check that out if someone wanted further info. I did recently stick a US Robotics 56k ISA modem in. The problem was there before and after.

Thanks again,
BH Davis