If it helps at all, for the install I did around the 15th, registration info was stored in AppData folders for both All Users & [UserName] - look for the Leawo folder. Registration from the 15th was still good, so I can't confirm 1st hand that the key they sent me today via e-mail worked.
I clicked the link on the GOTD page for the Leawo Blu-Ray Player page, then clicked the link to get it free. After entering an e-mail address the key was shown instantly, & seconds later I received an e-mail with the new key & a download link. I did not run the GOTD version [I confess I didn't even un-zip the download], so again can't confirm 1st hand it's trouble free.