This is because you have installed the patch when V1.2 was already on you'r game, The combo of "Tropico and Stronghold Classic" already has the patch with the game..
To fix the game you must reinstall it, But don't worry about losing you'r maps, Just move them into a seperate folder by doing the follows..
Create a new file called "Stronghold Files" with sub folders like "Maps" and "Saves" and move you'r maps and saves into the folders..
To see if you have V1.2 BEFORE you install the patch, Open the game and at the main menu look at the top-left of the screen and there will be text that says "V1.?" If it say's V1.0 then you can download either of the patches, If it say's V1.1, You can download V1.2, However..
If it say's V1.2, You don't need to download or install the patches, If you did download and install the patches when you have V1.2, Read above for how to fix it..
The reason it has this error is because if V1.2 is already installed, Installing it again cause a overwrite of the current files, That means the code of the files that were installed for you'r game had been changed and caused a code error inside the game and caused it to not be able to detect the CD..
Skills: Can shoot 2 bow's at once..
Weapon: Custom made Bow..