Basic troubleshooting:
1) try more than one monitor
2) Do you see ANYTHING on the screen (BIOS prompts etc) when starting?
Here's a cool test:
1. burn a copy of Ubuntu to boot to
2. Make sure the BIOS is set to boot to the CD/DVD drive first (if you can't even see the BIOS it's a hardware issue)
3. boot the Ubuntu disc
*booting to Ubuntu from CD avoids both a hard drive AND Windows completely. If you can boot to Ubuntu and things seem to work, then you likely need to reinstall Windows or use Linux (i.e. Ubuntu) instead.