I have a Dell xps 420, bought in 2008, 4 months later motherboard, video card had to be replaced. Am having similar problems now, diagnostic lights 1,2 and 4 light up with fan a high speed. What to do?
If the board or windows setup is giving you problems, about all you can do is try to clean the video and cpu fans with a canned air product to be sure they're turning properly and cooling your components. The dell case has few options for extra cooling. If your system won't post, you can try changing the power supply first, then the motherboard. It all depends on your patience and level of experience. Your dell board is btx, and very expensive to replace. It's a very nice setup, but dell doesn't always provide adequate ventilation or cooling of the inside components.