It could be a bad display on the laptop. I'd go ahead with the reinstall, and if that doesn't do it, call up Dell and complain. Make use of that warranty. You don't even want to know what it would likely cost to have a display replaced on a system out of warranty.
Okay, I just bought this Dell Inspiron laptop and I am noticing that the colors everywhere appears so dull. I've tried everything from colors settings to brightness. Nothing seem to work. I'm very close to reinstalling the Vista, since a disc was included. Help?