fsx, acceleration installed, 2 graphics card, fsx says invalid hardware at startup

i was wondering if anyone has seen this, and knows a workaround.what i found, is if i disable the two monitors on the second graphics card (7800gtx), leaving the primary graphics card (8800gtx), fsx starts fine.i'm guessing that the 7800gtx is too old, and doesn't support dx10, or shaders 1.1 or something like that, and the 88gtx does.is there a way in the fsx.cfg file to tell fsx, only pay attention to the 8800gtx, and to ignore the 7800gtx?jd