ok when i start LFS and play i press the gas pedal but i dont move at all.... but in NFS:MW i can drive fine.....please can anyone help me?

Have you assigned the pedal axis correctly?

taht clears it up but how do i do that. i know u go into options-controls-axis but which do i asign throttle and brake to?

Go into the game, and goto Options > Controls and click on the button Axes/FF.

On the VERY right you should see things moving (bars) when you press and depress the pedals, also steering the wheel too.

When you press the pedals, which way does the bar go? To the left or right?

ok its Number 4 Y-Axis when i press throttle pedal it goes to the left when i press the brake it goes to the right

Ok the bars should go to the right (from the left side). So that the bars 'fill up'.

For that axis number, to the left of that bar graph you should be able to click the assignment for the throttle, then it wants you to select an axis to the right (where the graph is). Choose the axis for the throttle on the right, and you should now have your throttle assigned. But since the bar is going backwards, you need to hit that Invert 0 button next to where it says Throttle. It should change to Invert 1, and then your Throttle should be correctly assigned.

Do the same for the Brake assignment, and you should be good to go.

ok i got the throttle working (thanks) but which axis do i asign the brake to? ok i did it thanks for the help tweak

Also sounds to me like you are using combined pedals as well. If so (pedals are using the same axis, one way for throttle the other for brake) make sure you have "use combined pedals" UNCHECKED in the wheel driver or Logitech Profiler if you use it, and LFS is setup on "separate pedals". If already separate, disregard above.