EDIT: Just saw that there's a whole sticky about this sort of thing, I just must have missed it by jumping straight to this section of the forum. Thanks to MacAdmiral as well for pointing it out. Still, if anything about this combination jumps out at people, it could be useful.
My father recently got all the parts for a new homebuilt system, and after putting it together is unable to get any video. I'll see the box myself in a couple of weeks, but I was hoping that someone might have some idea, maybe based on the hardware, of possible problems.
The only further technical details I have are that the fans apparently all start up, and that the case has no speaker and so there's no startup beeps. Also, my father works with electronics (just not computers) professionally, so I'm relatively sure it's not something not plugged in or equally obvious. But even obvious suggestions may be helpful.
As far as seating and power connections, it's probably the first thing I'll check once I get to see it myself, so it's not at all insulting. I've had more than one occasion when I've jumped straight to the difficult fixes when I've forgotten something like power, so pointing out specifics is good.
For switching cards around, I think he mentioned putting his old card in there, and getting the same problem. Of course, without power or proper seating the same problem would be there, but as he put it back in the old box properly it'd probably be something else. There is also the chance that the old card was too old; don't remember specifics other than it having 256mb ram. I have a very similar card that I know works, so I'll be able to switch that out eventually.