Final Fantasy XI does not boot!Follow

This isn't a personal problem, as my FFXI works fine.

However, a friend of mine is having problems with a newly installed FFXI. We're both returning players and we don't know what's wrong.

When he boots up PlayOnline, it boots fine. However, after hitting Play to start FFXI, the screen goes to fullscreen, turns black for about a second, and then exits to the desktop. PlayOnline doesn't pop up, no error window, nothing. He's checked his files, reinstalled POL and FFXI, cleaned his drivers, and nothing has worked. FFXI has worked on his computer before, however he has since formatted and installed new HDs. His other DirectX games all work, so it couldn't possibly be a problem with that. He has a Dell XPS, and consequently the GeForce 6800GTO. Seeing as how Square-Enix had a deal with Dell a few years back regarding FFXI, I dunno what might be wrong.

Any help is appreciated.