VirtualStore is a security measure on Windows operating systems included in Windows Vista and later versions of Windows. Sometimes, COS files will be stored there which can create issues when loading the games.  These persist even when you think you have deleted the COS file.
To find the VirtualStore folder, go to:
- C:\users\<username>\Appdata\local\Virtual Store\ and go to Program Files or Program Files (x86) and continue browsing until you find your Creatures folders. You can then delete the offending COS file and try again.
Appdata is a hidden folder, which you need to display if you are to browse its files.
The Map Editor will also export metaroom data to the VirtualStore bootstrap.