Hi,
as you read the page of SmartPropo, you will see, that originally ist is designed to only run with W2000 and "sometimes with XP" (words of the author

.
The error you get is caused by a device in your computer called "unimodem full duplex audio device" (or "..half duplex.." as in my case).
Be sure to read the manual for SmartPropo on
Go to your hardware manager, find this device under topic "audio, video and game controllers" and delete it.
Don´t be afraid of doing so, this should do no harm to your PC. My system reinstalls this device ever and ever again on the next boot (I have XP of course).
It is not enough to disable it.
Gruß Harald
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Modellbau&Elektronik
www.harald-sattler.de