Didn't fix the problem. I've got the Connected User Experiences and Telemetry service disabled and I still see CompatTelRunner.exe taking up to 100% of my disk usage for many minutes after startup. Incidentally, another way to disable the service is to
open a Command Prompt (Admin) and enter the following command:
sc config diagtrack start=disabled
Don't forget to stop the service if it's running:
sc stop diagtrack
OR
net stop diagtrack
You can always verify that it's disabled by hitting Win + R and typing services.msc to open the services dialog and scroll down to Connected User Experience and Telemetry.
But, alas, disabling this service, no longer resolves the problem. We need to discover what else starts the CompatTelRunner.exe program.