Maxvorstadt: Deinstalling and installing again doesn`t help. the launcher still does not appear!
By looking in a file named "Game" I found the following entry:
Resource error: : Could not find file: C:/GOG Games/Hammerwatch/assets/levels/menu_4.xml.bin
In fact, there is no assets folder at all, but an assets file, a file named "assets.bin".
Do you happen to have any overly aggressive antivirus software installed? If so, please turn it off for the time being, uninstall and re-install the game with the antivirus software turned off and let me know if that makes a difference :)