I've extracted the patch from its ZIP file, but I can't install it because it tells me that I don't have the original version of the game installed. I just bought the game yesterday. Can you help?
In order to fix the issue, uninstall the game (Control Panel > Uninstall a program) and run CCleaner or Advanced SystemCare to make sure that there are no leftover rogue registry keys in your system. After that, reinstall it using the serial key received when you purchased and try to launch the patch. If you still receive the same message, you will need to contact the game provider.