Cannot exit Google Device Manager Installer
I assume you installed Google Apps Device Policy. Then you need to follow these steps from the official Google support site to uninstall and unregister yourself.


  
  Open Google Apps Device Policy on your Android device.
  On the Status screen, touch Unregister for each account you have registered with the device.
  Depending on your device, go to one of the following:
  
  
  Settings > Applications > Manage Applications
  Settings > Apps.
  
  Select Google Apps Device Policy.
  Touch Uninstall or Disable and then OK to remove it.
  
  
  Alternatively, you can deactivate the Google Apps Device Policy app and then uninstall or disable it:
  
  
  On your Android device, go to Settings > Security.
  Touch one of the following:
  
  
  Select device administrators
  Device administrators
  
  Uncheck Google Apps Device Policy.
  Touch Deactivate.
  Touch OK.
  Depending on your device, go to one of the following:
  
  
  Settings > Applications > Manage Applications
  Settings > Apps.
  
  Touch Google Apps Device Policy.
  Touch Uninstall or Disable and then OK to remove it.