mazahito: During GOG Galaxy and F.E.A.R. Platinum installation, I've encountered problem as topic says. I'm using 64bit Win 10. To resolve it, do the following:

1) Click "Windows key" + "R" -> type "regedit" in the search -> User account control, click "Yes"
2) Locate: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
3) Copy those four folders under "ProfileList" to your C: drive folder for backing up - DONT LOOSE THEM!!!!
4) Delete those four folders+empty your Recycle Bin
5) Reboot
6) Install GOG Galaxy w/ Admin Rights+log in to your account. Install should work without error messages.
7) Install F.E.A.R Platinum using GOG Galaxy client. This worked best for me. Open GOG Galaxy always w/ admin rights.
8) Try playing the game. With this method also saves should work, worked for me.

Now, if you want to recover your Windows to the previous state, simply add saved FOUR registy entries into RegEdit by importing them into the system. After import, reboot and your system should get back to normal state. I dont know what causes that error message if you want to install the game in "normal mode" - experts can enlight me..?

NOTE: MAKING ANY OTHER REGISTRY CHANGES CAN DAMAGE YOUR SYSTEM - BE CAREFUL AND ALWAYS MAKE COPIES TO ENSURE YOU CAN RECOVER!!!!!