Hey there, I'm trying to do the same thing. I'm still collecting materials I need to construct my setup.
The MBP camera can indeed see infrared (apparently almost all CCDs can). When you're in Mac OS X, open up Photo Booth and point your LEDs at the webcam. You should then see if and how effective they are since the image you see on screen should appear as if you were shining a dim flashlight around, since the webcam picks up infrared as a light source but displays it onscreen in the normal visual spectrum.
If you're not sure if even that is working though, point a TV remote control up close to the webcam and press some buttons, like holding down the volume-down button for example. You should see the end of the remote flashing on the webcam image.
If that's working, then there's no reason that FreeTrack in WindowsXP wouldn't see it too. I'd suggest fiddling with the FreeTrack camera settings to see what you can manage. Also, don't forget to try dangling an infrared passthrough filter over the webcam lens -- this will filter out most visible light and only allow infrared to pass through. Most people here seem to suggest using film negatives stacked 2-3 times or the dark magnetic floppy inside of a floppy disk.
Feel free to PM me and we can track each others efforts! I'm going to do some tests tonight.