Ur useing the right software.. (there is more but what you have is good) and I dunno the stock clocks on the FX 5700 and i'm too damn lazy to go look em up at 3:30am, but if the game just like totally crashes start backing off your core clock by like 5mhz and see if that helps. If not then keep backing off things, or add more cooling.
As far as cooling, just try to have good airflow through your case... make sure it's all nice and clean
Also you can try adding extra fans to blow cool air onto the card... You could also use a different vga cooler thingy... that would help but it may be a bit much if your just starting out. Good Luck!