The check list for this are,
1. computer not boot.
2. graphic adapter
If your computer has a built in pc speaker, it should gives you one single short beep when it boots. Also check on lights, and wait for a moment until your OS loads. If your hard drive light flashing after a few moments, then your computer boots properly, and we can eliminate problem number 1.
But for the most situation, the problem lies on faulty graphic adapter.