Comp starts up but the screen has no sigal

Hey everyone, i have a huge problem with my computer i booted up a game "battle field 2142" then a little bit into the game the computer completely freezes so at first i thought okay whatever but, after attempting to restart it the computer would boot up and the screen won't get a signal and im completely stumped first off everything seems to be running fan is louder than normal like the comp can't stabilize or something im not sure. ive tried numerous things like unplugging then hitting the power button for 30sec to a min didn't work ive tried cleaning my computer inside and out ive tried the eraser trick ive tried different monitors ive tried even adding more ram into my computer...i get a feeling that it could be a mobo problem. Any solutions to this? or am i doomed to get a new mobo or just buy a new computer? any suggestions or help would be greatly appreciaed im purely desperate at the moment