Installing on D drive shouldn't be a problem at all.
Installing as admin and running as normal user is a problem, so is the reverse.
I doubt there is a 2nd running trainer process with the RXP GTN, but can you please open task manager like shown on the video (CTRL+SHIFT+ESC) and let me know if this is the case as well for you?
99% chances the problem is the Intel chipset:
Intel integrated Graphics vs Discrete Graphics card
The Garmin trainer GTN Simulator.exe process mus
Intel Integrated Graphics vs Discrete Graphics card (NVidia/AMD)
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