So at the first check what 5850 is it. It's one of most powerful graphics card from AMD to 7850 which is little better in tests. What's wrong with Q6600? 2,4 per CPU, 8MB Cache L2, dude.
http://forums.steampowered.com/forums/showthread.php?t=2766754 - this guy runs Arma on laptop with 45-50 FPS in multi. His GPU is shitty integrated.
Comparisions:
http://www.game-debate.com/gpu/index.php?gid=773&gid2=419&compare=radeon-hd-7670m-vs-radeon-hd-5850-1024mb
http://www.game-debate.com/cpu/index.php?pid=870&pid2=19&compare=core-i5-2450m-2-5ghz-vs-core-2-quad-q6600-2-4ghz
You can google maany examples, where someone runs Arma at hight details with higher FPS count.
http://www.moddb.com/forum/thread/arma-2-ultimate-tweak-thread(Q6600 and older GTX 260 than mine card).