32-bit or 64-bit?
What message did you get when you tried to register it?
Did you do so using 'Run As Administrator?
In case you misunderstood how to register, see this link for both the file & instructions:
http://www.dlldownloader.com/fpdtc-dll/
If so, rather oddly if it was previously registered on your PC, it sometimes works to unregister it then register it again.
If it still fails after this, & especially if you have 64-bit Windows, I think you are out of luck