Sounds like the screen's LCD connector (inside) got pulled out somehow, or came loose. This happened on my first iPAQ, and when I tryed to fix it, it all was working, but then I accidently broke the little black 'clip' that holds it down.

when that happends, the only way to fix it is, to get a new motherboard, or have some techs put a new screen connector on the board.
Anyway, with the screen connector out, the usually are a bunch of horizontel lines, about 3mm high each, and are different colors, correct?
The best thing to do would be what the other guys said, just call Dell and get a replacement.
Adam