Not sure if there was a practical fix already but looked on google I think most 1.5 patch support requests with wrong cd error from Total War Center.
But nothing had a solution for it (which worked for most people other than buying the steam version)
This is the solution;
So first I installed the UK gold 1.5 patch for it, since my gold medieval 2 box had PEGI on it. (if you're reading this looking for a fix you need right patch version for your retail box)
After that I installed this one:
http://downloads.sega.com/totalwar/m...-2-gold-dd.zip
Because the 1.5 update was already installed this one will take about 1 second but changes something which fix the missing link I guess.
Problem solved.
Not sure if a 1 step solution was already found but hope this helps.