To restore an Android emulator to its initial, default settings, you need to find its “image” file on your filesystem and delete it. The image file will be found in your $HOME/.android/avd/<avdname>.avd folder.
For example, I was just working with an AVD named Nexus_6_API_21, and its directory on my Mac OS X system is /Users/al/.android/avd/Nexus_6_API_21.avd. I moved into that directory and found several “.img” files, deleted them, and then restarted the emulator, and it went back to its default settings.
