Posted 03 July 2006 - 09:38 AM
I've had this happen to me on a couple of occasions and both times it was a problem with the graphics card. Solved simply by opening the case and reseating the card (don't forget antistatic kit!!) If the computer doesn't detect a graphics card at startup, it seems to simply halt the boot process (I guess it figures if it can't display anything. there's not a lot of point in continuing). You should also hear a number of beeps from the system speaker. These are actually an error report indicating the problem. There should be an index of them with either your motherboard or BIOS documentation.
Hope this helps