xbox to pc controller problem

Ok, i recently bought a usb adaptor that allows me to use my xbox controller on my pc.
Now it works fine, i got the drivers and its grand.... however, i plan on using it with GTA:VC, and this is where my problem arises.

Anyone with an xbox will know that the shoulder(???) buttons are not buttons you just press, but are pressure sensitive, so the harder you press the bigger the reaction.
Now, on my PC, these buttons are being picked up as an axis, as if its a d-pad.

so in GTA, the two buttons are in control of the camera, and so keep spinning unless i hold them both exactly half way in, which is a bitch and a half to do. I cant seem to change them in the controller setup in the game, nor can i disable the buttons altogether.... so can anyone help???

Flogen