Well seeing as you just reinstalled, your settings are probably different from what they were b4. So first off set all your settings to low and take everything off that you dont need.(I no the quality will suck but hey get a better video card lol). Also if your computer is in a compacted area like closed off and doesnt have proper fan that could cause lag also.(comp needs to breath to). So just open the door thats closing it off. Also you can take all the texture out of the game so everything is like a whitish snow color but alot of the lag goes away. If you want to no how to do that just ask cause my hands hurt.