Your system configuration is good. check what type of RAM you have on the system (DDR RAM or SD RAM)(DDR is better for games). Also, check the VGA RAM, how many MB and what type.
your problem i think is because you have less RAM on the VGA card, or slow RAM type is installed. where it gets full fast, and then it has to dump the data to be available for new ones. that's why it hangs.
XP is not a problem, i have XP and it is working perfectly