In order to fix “Invalid CD Key” error in Sword of the Stars Complete Collection, do these;

Fix 1: Edit “42890_install.vdf” file manually

• Copy your CD key.
• Go to Sword of the Stars installation folder.
• Look for “42890_install.vdf” file.
• Edit it with any text editor (I prefer Notepad++).
• Find “%cdkey%” and replace it with your CD key that copied before.
• Open Windows registry editor (Win + R).
• Navigate to HKEY_CURRENT_USER > Software > Valve
• Look for “TestApp42890” and delete it.
• Launch SOTS again.

Now you won’t see “Invalid CD key” error message again 🙂