Yea, well, best buy is good not much...they know nothing.
It'll run; it just won't be breath taking. All the gaming systems that most everyone here has are set up to run games on full settings w/ max quality. Anyways, you already have the game right? Just instal it and run it...lower the settings to the lowest limit, and then start kicking the settings up 1 by 1...till you find a good mix of no lag and detail.
AMD Newcastle skt 754 3000+
Elitegroup 755-A2 ATX motherboard
512 DDR RAM
120 gig PATA Hard drive
128 mb AGP 8x ATI Radeon 9250
300 watt 12 volt psu
Antec SLK 1600 case