Earlier whilst playing half life 2 i noticed my resolution had changed from the usual 1024x768 to 800x 600. So i went into options to change it back but accidently selected 1152x864, it then came up with a screen displaying "Cannot display this video mode." However the resolution did not go back to normal it stayed on that screen. I have tried everything to get rid of it, , as i cannot see where options is to change the resolution. i have re-installed it 3 times but that has not made any difference. Any suggestions are greatly appreciated. thanks!