list your full system specs and report your fps

no one is going to address your question when you do not ask properly

4310-gta-iv-artwork.jpg
 
GTAIV does not support physX, huh? hold on there..

I cannot answer your question until I at least know which psu , driver version, resolution and settings you are using? any overclocks, etc...!!

do you have a windows aero enabled theme?

you see it could be a bunch of things but so by providing no info it gets us no where

lets see what you decide to do next....
 

PhysX is not the only physics engine used in games. It is only used in a handful of games. GTA4 is not one of those games.

As a user above mentioned, GTA4 is just a bad port of a console game. Nothing is wrong with your setup.

You can try to drop some settings a bit and see what helps.
 

maskills24

Honorable
Jun 15, 2012
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Sorce engine= best coded, GTA 4=worst coded. A potato can run hl2 but a pretty good gaming rig that could play bf3 on high no issues can barely pull 50 on gta 4... Im hoping gta 5's lead platform will be pc this time around :/