The 7600 GS IS a low performance video card. It may have been a decent card on the low end of gaming cards almost 10 years ago, but by anywhere near modern standards, it's very slow.
But CS is an older game and should run fine on that card. What are the rest of the system specs and what did you try already? Has the issue always happened with that game? Are you only running the game or doing other things like watching videos, recording, streaming, etc...?