I don't think you understand what SSPhones is telling you.

You can get all the new features and Voicemail by upgrading just the MPD card to an IPEX.
And change the sets as time goes on. Instead of dropping 16K at one time.

My customer are very happy that there orginal investment is safe. I have people with phones from 1980 with the new IP phones, Who else can do that

Why did somone mess around in the DOS anyway.
If you want the software disk I sure if you contact a local Telrad Dealer they can sell then to you. If you can't find a local Telrad dealer PM me with the Version of the system and I will sell them to you.