From what I just read, rts.dll is the file with the copy protection and he should only get the message on an copy. Are you sure he bought it?
If it's a legit version, he could try the latest patch and hopefully it will fix the problem, otherwise he can go to
www.megagames.com in the trainer section, and there he will find no cd patches, and from what I've read, they come with a fixed rts.dll