Hp pc fan start working the i do not get any display

I have a hp pc I have inserted a NVIDIA graphic card 2years back now since 2 month
i am getting following problem.
1) i switch on the power button only the fan start working the i do not get any display nor any sound.
2) If i remove the RAM and switch on the power button then also don't get any beep.
3) when i remove and insert the RAM 2-3 times then the PC starts working.
4) the frequency of problem increases when i play games of more then 2hours of day.

please tell me what is this happening and please tell its solution.