After having downloaded the game (with all 5 parts) during in stallation I get this message (see photo) anyone know how to get around this?

I realise this is a necro reply at this point but if you still have issues perhaps it would be beneficial to try to redownload the files and try again if nothing else works.
Also make sure that:
1.You have same permissions for all related files
2.Your antivirus is not blocking any of the files
3.You have not renamed any files
4.Files were properly downloaded (it is entirely possible for files to get corrupted during download and still not throw any error during download nor stop the download)
Also make sure you are running the setup software with elevated permissions (such as admin or custom allowing you to have full control of both files and install location).