OK, I figured out.
As I understand, for WME, packages are not folders. (Am I correct?)
So using Game.AddSpeechDir("greek"); points to nowhere when I compile the game (allthough it works in Project Manager with F5).
I had to add a subfolder to the package.
This is what I did.
Make a package named "greek".
Add a subfolder to this named "voices".
Now I use Game.AddSpeechDir("voices"); This way it is working fine.
More with this.
Make a new package named "english".
Add a subfolder to this named "voices".
Compile the "english" package.
Now if I replace the greek.dcp with the english.dcp, I have my game speaking english. Cool
Spyros