Hey
What Igo Kyu writes is only half true... Before you upgrade anything, please go trough this:
http://theairtacticalassaultgroup.co...t=5058&p=52711
Install those patches, they should improve your performance. Also if you have further quetions, I recommend asking them at the ATAG-Forum. As this game was abandoned by the developers, the ATAG-Forum has become the place of the community... you won`t get that much advice over here...