C disk-> Program Files -> Sega -> Medieval II Total War-> Data-> World-> Maps-> Campaign-> Imperial Campaign-> descr_strat-> Then you change the files that look like this ----

Playable:
England
France
HRE
Spain
Venice
End
Unlockable:
sicily
Milan
Scotland
Byzantium
russia
moors
turks
Egypt
denmark
portugal
Poland
Hungary
End

You Change this so it reads
Playable
England
France
HRE
Spain
Venice
sicily
Milan
Scotland
Byzantium
russia
moors
turks
Egypt
denmark
portugal
Poland
Hungary
end
unlockable
end

You can also edit other files within the files but create a backup file just in case your game doesn't run anymore so you can switch back the original file.