computer loading problem (with pic)

I recently pulled my older computer from the closet so I could set it up for my parents. I plugged in the monitor/power cord/mouse and keyboard to make sure it starts up and lo and behold.. it does not. I cleaned the insides with compressed air and made sure all the hardware was plugged in firmly.

The computer does load, but only to the screen that shows the IDE card loading the hard drives that are attached to it. here's the screen..




The NOT DETECTED line is from a cd-rom I removed earlier and put on someone else's computer. After this screen, it turns black and that's it. The monitor is still on, but nothing.

What could be the problem here?

Thanks