There are no official drivers from Sony for the PS3 Gamepad for Windows.
But there are unofficial ones: http://www.motioninjoy.com I guess these are the one you probably use already.
In the Driver Menu there is a option to emulate the Xbox360 Gamepad so that you can use your PS3 Gamepad with games that normally only support the Xbox360 Gamepad.
If this doesn't work, there is a another Xbox360 Controller Emulator: http://code.google.com/p/x360ce/downloads/list
Just unpack in the game directory and configure the Buttons/Sticks for your Gamepad.