I just got new notebook, with Windows 7, ATI Radeon HD 5470, desktop max resolution 1366x768. When I put cs into 800x600, it wouldn't run in full window but black stripes would appear at both left and right side of the screen. Does anyone know how do I make the cs go into full screen mode?

I also noticed that changing my resolution in windows desktop causes the same thing so it's not a cs thing but the graphics system is sort of not allowing lower resolutions to simply stretch out to the whole size. Any help pls?