Display Issues on P4

I have p4 3 ghzsomething 1gb ram, 120Gb HD, leadtek 7300gs card. Quite recently i was having freezing issues which was due to my graphic card heating up since there was too much gunk in its cooling fan. Yesterday While doing normal browsing my pc rebooted and when i turned it on the monitor wouldnt display and showed the standby indicator (orange). I tried plugging in my monitor to the built in graphic card and there wasnt any display (The bios setting was set on auto detect for the video). i removed my graphic card (the 7300 GS) and then connected to the built in graphic card and there was finally a display, but after browsing for exactly 5 mins the pc rebooted again and now there is no display. I know its time to get a new pc but i would really like to know why this happened what are the causes.

you need to diagnose the problem by removing unnecessary parts like modems one by one and checking it

it is possible that two things are creating problems like your graphics card and something else

sometimes it happens to me all i do is clean my rams and graphic card and then all is A-one.

you need to clean out your pc,,i have to clean my pc regularly because i live near the sea shore and to much dust gets into my system, making it do wierd stuff..and yes that includes display problems as well,,i just take a cue tip, small brush and clean out my mobo, ram and system fans..etc

could be a software problem as well..what operating system do u have,,check to see if that is working ok..