If you sell your pscan on and the new owners laptop requires your old one to be deregistered, then they will be able to do it themselves.
You don't need to do anything.
The new owner inherits the support rights that you got as the original buyer, and, if they have any problems with laptop registration they can contact us and we will help them.
This is a 100% guarantee, and you can point any prospective buyer at this topic to prove that they will be supported.
I am also fine with you advertising your pscan for sale here on this forum if you want to.