Mostly high settings, but you need at least 1GB ram, and it depends what resolution you are running at.
I have a 6600GT 128, to get decent fps I play 1024 X 768 @ 72Hz, all medium settings apart from dynamic lighting and dynamic shadows which are off, no AA or AF, draw distance 100%. My Comp: P4 2.4 @ 3.0 GHz 1Gb PC3200 ram (dual channel) FPB 250 (system bus @ 1 GHz) Some ABIT peice of crap Mobo, 865PE chipset 80Gb Maxtor DimondMax 7200 rpm SATA HDD XFX GeForce 6600GT 128mb Also, BF2 performance is heavily dependent on the ammount of ram you have. Yes 512Mb will let you play it but it will be quite stuttery. 1Gb is the minimum you need for good performance, 2Gb to be able to play (providing you have a good enough GPU) flawlessly without stuttering.
i would of thought the 6600gt would run bf2 at all high settings exept for res and have AA and AF and shadows enabled, i get about 70fps with everyhitng on highest inc. shadows/AA/AF enables and on 1152*864 res, and the 6600gt is not that much slower than the x800xt pe, i cant run it at max reseloution, i think thats down to my crappy generic 2x 512mb pc3200 ddr 400 mhz ram.