Wacom don't share their user details with us, but they print the registration keys on the back of the plastic sleeve which the ArtRage CD came in. The number is 20 digits long, in fairly small type, and they call it a "serial number" which can be a bit of a gotcha. Hope that's of some help!
A couple of other important notes:
1/ You can update to the latest version once you've installed ArtRage either by using the "check for updates" option in the help menu, or by downloading the latest installer from www.artrage.com/artrageinstaller.html - This is definitely worthwhile doing as you'll get a bunch of new features and improvements by updating and the update is free.
2/ If you get an error message indicating that the tablet cannot be found, make sure that your Wacom tablet is installed, plugged in and that you have installed the latest Wacom drivers from their website www.wacom.com
Moving this to tech support.