Monitor frequency problem

I'm having some problems with the frequency in my monitor, I use a CRT, 1024x768, 85 heartz. and my resolution in counter strike is 800x600.
Today i try -freq 100 in my counter strike launch options, and the screen gets smaller, i don't know, like this
http://img513.imageshack.us/img513/1320/43386317.png

how can i fix it?