I was recently at a LAN, but unfortunately, my graphics card had just broken. This meant that I would have to make do with my onboard graphics card for the day. Call Of Duty always seems to be the most popular LAN game but luckily, it has a console to turn off additional settings so you can speed up the game a bit more.
With these settings, I was able to play a reasonably smooth game on an onboard GeForce 7050 and I must admit that lagging was not the reason I didn’t win.
And if the ` key doesn’t bring up the console, you must re-enable it from the options menu. It becomes disabled after your game crashes.

If you can't see the COD4 console
/sm_enable 0
This turns off unique character shadows to speed up the game quite significantly.
/r_drawDecals 0
This turns off details on walls and ground (such as rubbish). However, this setting may result in you getting kicked off by Punkbuster
/cg_brass 0
Your gun will no longer eject shells if this is on.
/r_drawSun 0
The sun will no longer be rendered, along with a few other atmospheric effects.
I know this has been up here for along time and over the past year I have used this many times… All I want to say is: you are god.
thanks – its nice to know there are others like me