Some original games do not work when a certain application has been installed, like DAEMON Tools.
When using Fixed Files make sure to use a Firewall which controls outgoing traffic, as some games call back to report the use of these modified files!.
When this happens use the original EXE to play online, else you could find yourself banned from the game!
Some No-CD/Fixed EXE files work fine in Single Player mode but are detected to be modified when trying to play online.
Always make a backup of the files that are overwritten by the File Archive, as the original files are usually required to update the game to a newer version or to play Online!.