It looks to me as though the computer isn't actually booting. You could try connecting a set of speakers to see if you have any startup sounds playing. I would also double check to see if the computer has both a video card and on-board video. If it has both, the on-board video is probably disabled, so you want to be sure the monitor is connected to the video card. Laugh if you want, but I've done this myself when I was rushing too much and spaced out.

Beyond this, there are all sorts of troubleshooting methods, but how much time, effort, and cash do you want to invest?