there is something wrong with your computer buddy
I have a dual core 2.4 ghz amd 2 gig ram, 7800GTX and at 1680 x 1050 i was pulling 99fps with max aa and af
I got a 8800GTS now have 3gb ram same cpu same resoloution 16x aa 16x AF and still get 100, in fact i limited the fps to 100
if your only getting 40 odd fps, check your power supply, ram timings, voltage ect as thats very down on performance
pm me your brands of everything , including ram, model no. ect of everything Ill help you configure things better im a IT tech
no one deserves to play lfs at 40fps that would be torture