Cast it aside. First person shoot 'em ups such as Call Of Duty are much easier to play on a keyboard and mouse than with a joypad. I remember when Quake 2 came out and I bought a gamepad to go alongside it. After a week I was playing only with keyboard and mouse, I got rid of the gamepad shortly after.
Persevere with the keyboard and mouse, you'll soon get the hang on it. I always reconfigure the up,down,left,right keys for movement. Left mouse to fire, right mouse to jump, wheel to change weapons. It's the only way to play it right.