Blank screen

Not with that tidbit of info. There are many reasons.
What do you see visually, (Lights on Cd, hard drive activity, etc)
How about the lights on back of computer ?
Look in your owners manual if they are not all green.
download one from DELL for your model if you do not have one.

Have you tried to boot into Safe Mode (F8) key at startup ?
Do you have an installation CD ?