I've changed from QT to OpenGL and now when X starts the screen is completely black.

I need to know how to chang back to QT from the command line (I.E where the config file is)

Thanks

I believe that it's in the DB. Try CTRl-Alt-F1 and see if that gets you a console prompt. If that doesn't work you can use one of the usual tricks to boot to single user mode or use the CD as a rescue disk. (this wiki page has info on doing this http://www.knoppmythwiki.org/index.php?page=BlackScreenAfterInstall) You can also use an ssh client (ssh under Unix/Linux, putty under MS-Windows, ...) to remotely login to the box.

Once you get a root shell session you can use mysql to change the ThemePainter value in the settings table.

Thanks, I'll give that a try.