How to change screen resolution.

Ok. I have a problem. I was playing Vanguard Saga of heroes when a Friend on steam Messaged me. it minimizes vanguard to open the message.Then i open up Vanguard again but when it tries to open Vanguard, it also tries to open the message. Then my computer crashed because of that. I start up my computer, and open it to find that im running 1024 by 768 for resolution! I have been running 1600 by 1800 (i think thats what it is) but then i open up the thing to change resolution and i cant go any higher. i have done google searches, yaho searches, looked through trouble shooting on my computer but i cant find anything! So I've come to you guys. Please help. (by the way im running 2 Nvidia GeForce 8600 GT video cards)How to change screen resolution.
If you can not increase the resolution even outside of VSoH, your graphics driver may have been messed up. Try reinstalling or updating graphics driver. BUT before you do that, try booting to SAFE mode then scan for virus. Something might have slipped through when you got the Message.