Why does GTA 4 lag on my PC?

Gta iv lag so much in my pc?

• i have powercolor 6670 2gb ddr3 video card processor: amd(tm) ll x2 250 3.00 ghz 2 + 1 gb of ram but my windows 7 64 bit read only 2 gb i don't know why power supply: hec 300w (i know it's low i will upgrade very soon) i play fifa 12 on highest setting and resolution and pes also without a problem also virtuA tennis 4 and the sims 3 but gta iv works very bad it lags a lot even on the lowest settings it still lagging is there something in my pc or it's the actual game problem ( my gta iv is pirated and i have a crack of it) thanks sorry about my english

• Answer:

  A pirated copy. That's your problem. The game (which is a poor port of the console versions) has been patched by Rockstar many times now, so it runs much better if you have the original copy.