Welcome to SF.
Ok a few things first can you fill out your system specs in your UserCP.
Do you have all the current drivers for your hardware? (Video,sounds,mobo,networkcard)
Did you install CSS from a CD or Steam?
Do you have a Anitvirus running and is it updated?
Also read threw this other posting on CSS we ran threw a few thing for it there about the lag and video issues. Counter Strike Source