Hey i got this problem last week, i took pc to fix at some place just for them to tell me after 5 days there was no problem. Today i woke up, went on youtube, and after maybe half an hour of pc working and youtube playing monitor goes black and i lose all the sound even though i was still on youtube when this happened. I restarted pc, everything was normal, i went to youtube again and after 5 mins of computer being active same things happen. Computer is old, fan can be pretty loud sometimes although a month ago i was checking the heat of my cpu and all other things and it looked normal. Could this be caused by a virus?