I'm trying to help my friend out here, and this has completely stumped me.
Whenever I turn on his computer, windows will load up (showing the moving blue bar and such. However, whenever it gets past that, it just shows a black screen for a second, flashes some message in a window (cant see what it is, it only appears for a frame) then goes back to black. After a few more seconds it restarts and repeats.

I have tried everything short of reinstalling windows. None of the safe mode options work. I have run Knoppix (CD bootable version of linux) and everything filesystem-wise seems to be fine. I cant understand what the heck is wrong. I dont even get to the login.

And suggestions?

Which Flavor of windows is it?

Windows XP home, I'm pretty sure he has SP2

Try booting to the XP CD and go to recovery consol and run a chkdsk.

Already did that. The HD is structurally fine, I'm fairly certain this isnt a hardware problem as Knoppix ran perfectly.

Have you hit the pause button at about the time the message flashes?

Nope, what will this do? (Didnt think it would do anything in windows.)
This is inside windows.. the mouse is working and it is a windows XP message dialog box. But nothing else works (Ctrl-alt-del even)

The Pause button will stop the computer just before it reboots...Little known key that has great diagnostic value.

Interesting. I'll try that (Will be a while, gotta go find him again.)