Hey can somebody help me........

I open a computer and checking a stabilization and realise that my computer will get hang after i open it around 6-7 hours.....before my computer were get hang....the CPU is coming out a sound "tick" once and when i move my mouse, i can't be moved any more......when i go to check at the System tools it said that i was restart the computer but i didn't ......My com is already used for 4 years but my others friends com wouldn't facing such this situation before as their computer were using longer than mine.....Can somebody tell me or suggest to me what is the problem and wat should i do....... plzplz
this is urgent........