=/\= Finding the game folder with the GOG Client:

1. Select the list of installed games
2. Select the game
3. Click the Settings Button at the top, next to ►Play
4. Select: Manage Installation
5. Select: Show folder

There should be a /base/ folder in that directory.
Open the /base/ folder and look for the last modified *.cfg file.

The cfg file has your Windows Account or Logon Name, example:
zeuz23.cfg

As mentioned by Berzerk2k2 you can simply use Notepad or the Windows Text-Editor, which is the same Program.

Just wanted to say thank you aswell, adding these five lines and rebooting the computer and it worked again :)

Forgot to say thanks that worked