Fixing a mate's computer

I don't believe this is the right section but I was unable to find one that would work for this topic.

My friend has a Gateway DX 4300-11 that broke as he put it so I asked if he would give it to me. I plug in the power cable and all the mobo lights come on. I plug in my monitor but get no video output. I take off the side and replug in the power and I see all the fans spinning non-stop and notice it's missing a hard drive. Keep in mind this is before I press the power button. I press the power button and nothing happens. I try to find a power button built into the mobo to see if the problem is the case but find none. I remove the mobo and CPU and they look absolutely fine. Any idea what could be the problem?

 

It sounds like a problem with the mobo, you dont always have to see physical damage