BFBC2 scales well on virtually any machine that has a decent graphics card and at least a dual core. They recommend a quad core, as it really does help with Physics. at a 720P res you will be able to run pretty decently. I would start with HBAO off and AA and AF turned down tp x2 or x4 and details on high. Some people prefer to turn the details on medium and turn up AA and AF, but that is preference. HBAO takes a hit on most systems because it is a lighting effect.
If I can play on a T6600 with a 4650 mobile with Win7 in DX9 mode and think it looks halfway decent, you will be fine. I also have a PC that has a 4GHz i7 and 5870 and it runs MAX and looks REALLY good. Basically the game looks Decent, good, very good, awesome, and FREAKING AMAZING. Even in DX9 with low it isn't a bad looking game. I have the Demo on PS3 and on a PC on low it looks better.