The monitor on My son's computer started turning off for no apparent reason. He didn't tell me until today and now there is no picture at all. The computer boots up and is running but there is no picture. The monitor goes to a yellow light. When I disconnect from the CPU, a color window appears on the monitor and tells me no signal, but when I plug back into the CPU, it goes black. One time,when I unplugged and rehooked cables, it came on and Windows booted and ran for about 5 minutes before the monitor went black again. I am running XP Service Pack 2, Windows Defender and Norton Virus. HELP! I am totally lost. Thanks

Try another monitor although it is most likely the graphics card.

Does the computer have an onboard VGA port or just a Graphics Card? Or only an onboard?

What is the make and model of the computer? Was a card ever added?