FxSound and DFX registrations are limited to a single PC.
The registration counter is a tool that we use to prevent our paid software from being shared to those who have not yet purchased. We understand that the counter is a bit confusing and this system for counteracting illegal sharing can be inconvenient to our paying customers, but a rash of piracy led us to need to implement new measures. We're working on a more reliable and pain-free system for the future, which you can look forward to in later updates.
For now, registration is capped at 3 for FxSound. If you ever hit this registration count and you have not been sharing FxSound to users that have not yet paid, you can contact us here to reset the count so that you can continue using FxSound.