Disable the "format disk" dialog

Solution 1:

There is suppose to be a way that works with Win10 by editing the registry where the Volume Identifiers are stored. A full description can be found here.

As a temporary workaround (or a final one if you don't get anything else to work) you can use a workaround though Authotkey. You can setup a script that immediately closes the format window after it comes up. Here is a description how to do it.

Concerning deleting the drive letter: I didn't try it, but you can also remove a drive letter using diskpart, did you try that option running diskpart with administrator privileges?

Another option would be to disable the autorun through the registry (so all types of autoruns are disables), here's an explanation how. But I'm not sure if this will effect the formatting dialogue.