Message "No Input Signal" on Screen

Am looking at one of my club members PC and after using his firewire connection the screen went blank and showed the "No Input Signal".
This PC has a separate graphics card and no onboard card so my first thought was the graphics card has fried! Tried 3 different monitors (all known to work) with 3 cables, no joy. I have just replaced the card with a brand new one and still no joy. I'm guessing it must be the motherboard. The PC is a Dell 5 years old. If it is the motherboard it hardly seems worth replacing. All data is backed up but I could always connect the hard drive to another machine if there is anything on it of importance that had been missed on the backup. Is my diagnosis likely to be correct or is there some other possibility?

Is there a spare PCI slot on the motherboard? I'm presuming not but worth a shot.

It is a PCI Express card and I think there is just the one slot but will look tomorrow.
Thanks

Have just checked and no there is no spare slot. I assume it must be the motherboard then?

It certainly sounds like it if you've tried a new GPU in there and a plethora of monitors and cables on both GPUs.

OK Thanks. The member has a laptop to carry on with and I will hitch the hard drive up to my system just to take off the email contacts and messages and anything else he has missed on the back up. Many thanks for your input!

I suppose as a last resort you could try re-setting the bios. Just remove the small battery from the motherboard for a few minutes. Be sure that the power cord to the PC is not connected when you do it too.