Excellent, got it working last night!
I managed to find a copy of TrackIR software 4.1.028 on the internet, which contains a 64 bit trackIR 2 driver. 4.1.038 on the trackIR website doesn't contain a trackIR 2 driver.
One needs to disable driver signing in Windows 7 for it to work, and install and use the interface from 3.13, so a bit of fiddling around but I'm chuffed my old hardware can still be used!
If anyone needs a copy of the 4.1.028 software and more detailed instructions just let me know!