PC game lag

I have a Windows Vista home premium computer with an NIVIDA 8500GT graphics card with 256MB, an Intel Core 2 Quad Processor Q6600 each core operates at 2.4 GHz, 2 x 4 MB L2 cache, 1066 MHz FSB. I have a 500 GB SATA II hard drive. Dual channel 2048 MB DDR2 memory, Memory Card Reader 15-in-1. I have a 32-bit operating system and 2030 MB of rams. My problem is, however, that I have constant game lag while playing all next gen gaming titles (offline). Games such as Bioshock, Jericho, Call of Duty 4, ect. I am not able to play these games on the highest graphic settings without lag, (sometimes not even fair graphic settings). I don't understand why. :confused:

Moar Ram!

u cud try 3gb of ram but 4 is pointless because 32 bit is wide and won't index all of it as usuable if i remember rite but tbh if 3gb don't work check ur system cos summin must be wrong cos it sounds good. i run a 2ghz dual core comp, 2gb ram and 256mb gfx card and it plays crysis well in pretty good graphics

ur graphics card could be the problem?
ur hard drive? wot is the read speed? cud be a few things really, lol

yeh probably need more ram as vista is a ram hog to the max.

Your graphics card isn't very good, looks like that is the first problem.

Graphics card is probably the problem , but may have too many proccess running in the background of your pc, so optimizing would be a good idea - End any processes that arent needed during playing a game...(zone alarm - big resource whore )
there are a few free ware programs and good one too start with is c cleaner*
give it a try, good luck.

(i know im late with the reply ;))

The 8500 is a awful card, and thats why you lagg... Not sure why you chose to put it next to some pretty good components. If you want a cheap good gaming graphics card get the ati 3850