Coby tv says no signal?

Okay today i got a Coby 22" TV, cable works fine, and Xbox works fine. But when i try to use my computer it loads Windows XP Loading Screen and Once it goes to log in Screen it goes to No Connection, i Can press down and Enter and i can hear it log in and it says no connection Its getting me vary mad that every thing else works Except the computer. I really need some help the VGA cable works perfect on my E machine Screen but for some reason it wont work. HELP