I was recently having small problems with my computer and i hadn't reformatted in a long time so i decided to do so. My Left 4 Dead game worked perfectly fine before the reformat but after it has started to lag and freeze up sometimes. Im looking for advice on what the problem could be. Just some stats.

Windows XP
800w power supply
2GB Corsair memory
Nvidia 9600GT graphics card
ASUS A8N SLI PREMIUM motherboard
Not too SURE of Hard Drive space but it is sufficient i know that.

Any help would be greatly appreciated.Start with re-installing your MBoard drivers from the MBoard driver CD...
Re-boot
Then install all your other device drivers.I will TRY this and let you know.OK.it made a GOOD bit of a difference but i'm still not running as smooth as i was before.

Sorry for the late reply i went on vacation.What version of video drivers do you have installed for your 9600GT?not sure whatever are the newest ones on there website.windows has default driver for that kind of VC. I am thinking that your you haven't installed the correct or INCLUDED driver in your VC.
here is what you can try:
1. install you Mobo's driver for its chip sets
2. restart then install your video card.

I hope this helps