Windows will recognize it via USB, but the PS3 controller will not send send any commands back to the PC until you send it a special USB command. Specifically, I believe it's HID_REQ_GET_REPORT. Anyway, I found a bit of source called sixaxis-init.c on the web. It basically is a bit of code that looks for any HID devices that match the sixaxis vendor/product ID, and sends the command to each controller. It does require that you have libUSB installed, and you have to install a filter for the PS3 controller (very easy, libUSB comes with a gui to install filters).
I had to tweak the code slightly to get it to compile, since I think this code was originally written for Linux. Mainly I thnk I just had to tweak the includes. But I've attached what I compiled. I'm pretty sure I compiled this using 64bit MINGW, so it will probably only work on a 64bit system. I included the modified source as well, so you can compile it on 32bit if you need to.
After you run this, press the PS button in the controller, and Windows should see it then. It exposes everything but the tilt functions. There is also some sketchy looking drivers you can download and install. They do give you access to tilt, and I think even bluetooth. But I'm a little leery of them.