Great to hear, that it is working now.
Older software should NEVER installed within the path C:\prgram files or C:\program files (x86), because there are some limitations on read/write permissions, even if the user account has full admin rights. Why? Simple, the username is not Administrator Sounds silly, but it is the case. At setup, there is a hidden admin account created (not usable, you can not log in to that account), that is always called, if an action requiers full admin rights (via UAC). Most older software can not work within this environment. But if you install the Software somethere else (say C:\Games), the limitations mentioned above do not interfere.
The installer sets "Run as Administrator" flags for the files s2gs.exe and sacred2.exe. This is due to compatibility issues, as the the game was originally designed for Windows XP. In XP, every software installed has full admin-rights, because the default account on the pc was always an account with full admin rights. Vista changed this with the UAC (User Account Control - this PopUp with "Are you sure to allow this" for everything). So, to let the game run smoothly, it needs full admin rights. As Sacred 2 was NEVER designed as a single player game, but has an offline single player, there is a server emulated everytime you start the game. The sg2.exe IS in fact the gameserver engine. Therefor, to let the game run at first and let it run smoothly at second, the gameserver itself needs full admin rights.
So, the installer tries to set the needed flags for the files but Windows 10 itself set these flags at first start of Sacred 2. If the installer finds the flags set already, there goes a call to windows to inform the user "Flags already set, nothing to do here". Why Windows 10 tells you this in the way it does? I don't know Maybe the gyus from redmond can tell you, but I doubt that. It is possibly, that this "error" comes due to some legacy compatibility back to good old Windows 95 or even DOS. Maybe it is some other thing. Maybe it is... a file with bad karma or high sun activity Ok, seroius, I just don't know, why Windows acts like this. Only thing I can tell you: It acts like it does.