Can't change resolution back

[imported_Nacelle]

I was setting up a computer that is hooked to a TV only. I am using a monitor to set it up. Then I will take it away when I done with the set up. It has a Radeon 9000 w/Catalyst 4.5 drivers. I set the dpi to the highest it would go. So things would be easily readable on a TV. And the rez is 640x480. Well now I can't see very much because of the low rez and the high dpi. And I can't get the rez any higher because I can't get to the bottom of the box where the apply button is. I also can't get to the advanced button either to turn on the ATI task bar button. I've also tried to do it in safe mode, to no avail. Any ideas?