i know many thing about the pc's hardware, and 512mb RAM is not enough in my sight. you need at least 2gb RAM to run the game on its best. and the 1.5 patch required it.a good vid. card. (i recommend Radeon HD 5000 to 7000) the radeon gives a 80% boost on the graphics ;D and a problem i had with another game, is that i need to install a stereo plugin, or hifi.
I hope you will slove the problem,
Kind regards,
Mike