Just use CheckAndSavePKey() with a new product key. That over-writes any existing key.
If the customer is already activated, then they need to deactivate first. Use Deactivate().
How to erase the key?
prashantDear Sir,This is a weird situation, one of our clients activated the software with the given key. Later on the order got cancelled, he deactivated the software and the key was deleted from the server. After few days again he decided to buy the software. He already had the setup, so he installed the software and tried to activate it with the old (now deleted) key. It obviously failed. We provided him the new key. But he is not able to deactivate it and not able to put the new key. Please tell us how to erase the old key from his computer in this situation? Is there any way? Last time this happened on Linux, I simply deleted the user and created new user on Linux and reinstalled the software. It worked. But this is not an elegant solution. Please advice.
