Key change causes beep and audio problems

[mindonstrike]

50% of the reason MTU provides a demo to try is so you can make sure the program will be compatible with the computer you are planning to use.

Maybe there is some small difference between the demo and the full product ? but there isn't supposed to be.
The prudent thing to do is resolve this issue before spending money on a program that may or may not work on your system.
Asking for a refund can be uncomfortable for everyone involved.

IMHO
Sam