Computer switches off

My computer uses Windows 98SE. Recently it developed a problem where after about 5 minutes a green line approximately 1 centimeter wide appears across the upper half of the screen. The screen then goes blank with the computer still running. When switched off and on the fans can be heard to run but the screen remains blank. It does not restart until it has been left off for several hours. I reloaded Windows but that does not help. Last night I took the computer apart and after that it worked fine. Tonight when I used the computer it was back to the same old problem. Can anyone help?

Thank you.

 

That sounds like a hardware problem, but i might be wrong. i say this because i think you said that it will reboot only after several hours, does it give you any beep codes, or do you know if your computer (any internal part) runs hot.

 

Someone else suggested that to me but I don't know how to check.

I was a bit surprised that it worked fine last night after re-building it.

 

you can use Mother Board monitor download Here
it is free, and very small, but not all mother boards are supported they need to have a WinBond chip on them.