This is an interesting topic.
What is this "mgr" that you mention?
We have a 4400 system with 4730 software (and CCS too for call centre).
I pulled a voice guide off the system and gave it a ".wav" extension. It played in media player, and I found what format the file was in.
I then created a wav and saved it in that format, I put it on the system.
However the system wouldn't see it, I assume the system needs the file added to it's database somehow, but I couldn't see how it was done.
In short, you can create the voice guide files in the correct format on any PC, it's just getting the system to see them.
I can give you the details on the voice guide format and how to convert using other tools if you like
Russ