Ok, it boots, another piece in the puzzle. Have you noticed you don't have as much ram? You are supposed to have what, 8 Gig, is it all there, check it. How many sticks? But check the Diag Lights in the back too.
You should also, burn your Dell Diags Boot CD, it should be in your DELL folder under DRIVERS. If not, download it from DELL, use the Auto-Detect System to find your machine, it will give you exact drivers. Download the Dell Diagnostics CD and burn it. Stick it in the drive and BOOT to it.
Then post your results here.