From the game forum:
In the game, my stalker automatically turns to the left and up...what do I do? It is (

Desert Eagle: Postal3, The steering wheel is accidentally unconnected to the computer? I had exactly the same problem in Dead Space because the steering wheel was connected.

Postal3: Now I disconnect... I had no idea what this could be from behind the wheel... anyway the glucose remained =((
Added in 1 minute
Oh, I had to turn off the guitar from Guitar Hero 3... now everything works perfectly, thank you!!! by Yahoo*