If you could add some details :

Operating System ? [ windows 2000 / XP / ?]

You SEEM to have ? Please clarify ? [ What were you doing ?]

If it's a windows box, then we'll talk you through how to uninstall the Graphics card drivers, then reinstall.
As it appears to be the problem ............

Just remember :
Learning is supposed to hurt
But next time : If in doubt : DON'T