If the software is still installed, keys are often stored in: HKEY_LOCAL_MACHINE\SOFTWARE\CyberLink\PowerDVD13 OEM Stickers:

Released in 2013, CyberLink PowerDVD 13 offered advanced 4K support and media format compatibility, but it is now outdated and lacks support for modern operating systems. While legacy CD keys might exist for the older version, current users are advised to use modern alternatives like VLC or the latest PowerDVD for security and UHD Blu-ray support. Explore the current version at CyberLink .