I have checked every single file on disk, there is no uninstall file. The classification as at risk (given by F-Secure) depends on the installed version of PowerDVD, it is 3.0. This version is no longer updated. The actual version is 8.0. And I don't see why I should buy the actual version not using this program for the future, too.
Now I didn't find any possibility of uninstall on the websites of Cyberlink. So I asked for a solution per e-mail.
Anyway, thanks for your answer!