resolution changes without user permission

I'm working on a dell computer, and it's got an ati 3850 graphics card in it, and I upgraded to a 650 watt power supply to compensate for the card. computer works well (just a few weeks old) but every time i play any full screen games (dawn of war soulstorm, diablo 2, etc) the games will play fine, but when I exit the game, the screen resolution will goto 800x600 and nothing i do short of restarting the PC will allow the screen resolution to go to the 1680x1050. newest ati driver and a fully updated vista are in use, and the acer 22" monitor driver from acer is also installed. does anyone know what the problem might be and how to correct it? Thank you for any assistance in the matter!
~Chris

 

have you tried completely removing the video drivers from the system and then reinstalling? Make sure you remove all the files or you may leave the problem on the PC

 

Are you using a launcher for D2? I had the same trouble until I used a 3rd party launcher.