Compaq 1200 locks up Intermittently

Hello,
Wondering if anyone can give me a suggestion as I've exhausted all my
own ideas:

Compaq 1200 with 256MB of RAM, 40GB hard drive. System is extremely
slow in all operations...not just Windows. Even slow getting into
CMOS sometimes. Slow lag response within CMOS also.

Most of the time, I can't even shut the machine down once Windows
starts. I shut the power to the computer off in order to do a
restart, and turn that power back on. WHen I go to restart the
machine, it will not start (no power at all). After about 1 minute,
it will start.

I've run tests on RAM, which come out all OK. ALso run tests on
processor, which turn out OK. Re-installed OS, re-formatted HDD, re-
installed OS again. Unsuccessful. Anyone have a clue?

Mike

Just to clarify, the model of the desktop is SR-1200NX.

Thanks!

Oh yes, and additionally, something I just discovered. When I check
the task manager, and look at CPU usage, all processes show 0%.
INCLUDING SYSTEM IDLE PROCESS. As well, the CPU usage graph shows 0%
usage, so nothing is doing anything at all apparently.

Mike