problems, GA-7VtXE+

Hi,
I bought a computer a couple of years ago with GA-7VTXE+ motherboard and
XP1800 CPU,
It has worked fine all this time until 2 days ago I can turn the computer on
only after several tries,
(I actually have to unplug it from the electricity)
it beeps not frequently and nothing happens, then it finally starts and
works OK for hours, and then
everything might freeze suddenly and takes several tries to reboot.
It is not related to overheating since sometimes it won't start even after
hours of break.

The system tempearture is ~41 C and Processor is ~54 C. The system fan shows
0 rpm but I think
it has always been this way, probably sensors are not connected.

Does anybody know what could be the problem?

Thank you

Vadim