Dell M4400 hangs at the welcome screen and during reinstall of WIndows 7...

So I will sum this up as quickly as possible. I have a background in IT and I've fixed and built plenty of my own machines. But this time I'm stumped. I have a Dell M4400 and I upgraded it from Vista to Windows 7. It was working fine and now it just hangs at the welcome screen when I boot it up. The pointer works, I can even tell things are working in the background because it downloaded and installed some updates when I rebooted it once. Even in safe mode it hangs at the welcome screen. 

Then it gets even more weird. I tried to reinstall windows 7 again and even did the repair install. The repair install didn't fix anything. But when I tried to go through a new install it hangs at the screen where I check a box and say I agree to the terms, etc. So that was really odd. I even tried a formatted drive and the new install hung at the same spot for the agreement. 

Up until these points everything works. The pointer moves, I can click, but when I click on the user icon on the welcome screen or on the checkbox for the agreement nothing happens. It's very odd. Anyways I have no way of explaining this. It apparently isn't the hard drive. I ran it through memory test, etc. So any suggestions would be great. Thanks guys!

Oh and I've ran chkdsk on the disk, and obviously tried another disk as well so I wouldn't think that's it.  I strategically disabled some stuff in BIOS to see if there is some hardware issue, no luck so far. I'd done the diagnostics, it found nothing, although in the BIOS diagnostics report it said PSA 4117 2000:8003 "Diag Not Found". So not sure what that means. Now it's attempting Startup Repair since it looped and died on startup. So my changes triggered something but apparently it didn't like them.  It's been "attempting repairs" for several minutes now, so we'll see. Any help would be much appreciated this is a really odd issue.