Computer won't boot, displays checksum error

My PC won't boot on being switched on......it won't display anything on monitor and the lights on

keyboard won't blink(they normally blink once on being switched on). Sometimes when i am lucky it

would start when i press the reset button after keeping the computer switched on for like 4-6 hrs(with a

checksum error).

I have already replaced the mobo battery with new one and i am still facing the problem.

Any idea how to fix it?