Wierdest Problem ever..

Ok im being paid to fix my dads work-mates computer. Ok so i clean all his spyware using adware, hijackthis and the stuff...Ok so i reboot after putting zonealarm in and after it says GATEWAY blah blah it displays a message saying:

Operating System is missing_

and stops.

what the???

So ok i power down, reboot and now nothing. the moniter doesnt turn on....absolutely nothing shows up, its as if the GPU has just died!?

Wierdd.....
Got any ideas?
I told him to boot it up tommorow after its cooled down (possible anti surge gateway something-or-other)
If it still does not show up, im gonna bring my PCI GPU and eliminate the grpahics card from the equation...

Wierd or what?

any ideas?

Maybe the boot record was deleted? Try connecting another hard drive with an OS to your dad's PC with the jumper on master, while running the original HDD in slave.
This type of thing has happened to me before but I didn't really look for a solution. I just copied files from the HDD and formatted over.

I cant exactly do that because the screend oesnt turn on!

Just curious...you said it was a PCI card...have you tried blowing the slot out with a can of air...even some of the smallest dirt can causes issues like this...

Seeing as its an old Gateway(judging by the PCI GPU), there is always the possibility that the CPU or the memory could also be crapped out. If the vid card isn't the problem you'll have to do some more investigating. Is the mobo getting power? Vid cable OK? Monitor working correctly? CMOS battery still functioning?