PC Failing Fast...Need some help!

I need some help, and I will do the best I can to describe the
problem, but I'm not a hardware techy, so bare with me please...

I have an old P3 running Win 98 that has worked without problems for
several years now. Two nights ago, the mouse stopped working while I
was using the computer. I was able to reboot with a ctrl-alt-delete
on the keyboard and the mouse worked fine.

Then last night, booted up and walked away from the computer. Came
back, mouse not working but keyboard is. On reboot it said no mouse
detected. Tried working inside the control panel from the keyboard
for a while, then the keyboard stopped working. On reset neither
mouse nor keyboard worked. Reset again and got keyboard back. Did a
cold start and got both back temporarily, then lost both again after
several minutes. When this happens, the computer is still functioning
(if I'm in a process, the status bar keeps moving forward, so it's not
freezing up). I was able to run a virus check and several other
utilities in between reboots and failures. I started recording some
recent files to CD last night and left the computer running to finish
the process.

When I got up this morning, it appeared as though the CD recording had
completed, but of course the mouse and the keyboard were not working
so I had to do a reset again. This time, the machine made noises (not
sure if from the hard drive) that it didn't used to make. The start
up beep was week and sickly sounding. It ran through scan disk and
went to a black screen with a flashing cursor (no prompt). I reset
again, again with the noises and sickly beep, this time it booted into
safe mode. Mouse and keyboard worked for a minute in safe mode then
died again. At this point I've just shut it down completely.

At first I thought perhaps the PS/2 ports were failing, but with this
further degradation of the system, I'm now thinking it must be
something bigger…I'm really hoping this is a mother board issue and
that my hard drive data is salvageable....any chance of that? Any
suggestions on what to do next? I'm at a loss, not sure where to go
from here.

Thanks for any help you may give.
Becki