Strange monitor or bad luck?

Hello,
my monitor recieves signal from my laptop but not from my PC so I assume my pc has a bad vid card or something BUT here is the interesting thing.

my friend sent me a refurb pc that worked when he tested it. He mailed it to me and the monitor did not work when he sent it to me.
We installed a differnt vid card and the problem was solved, then the next day the monitor goes blank again. I checked all the conections and rechecked the monitor (still works on the laptop) . but no luck. I gave up and bought a second refurb PC.
I set it up and it worked fine used for a few hours then shut it down for the night. this mornining I tried to turn it on and the SAME THING HAPPENED AGAIN. the pc it running but no signal to the monitor, it still works when plugged into the laptop.

is there any possibility that my monitor is cuasing this problem?

Regards