Restore full access to C: on Windows after turning on/off UAC

After installing Windows 10 and disabling UAC I was able (as a user from the local Administrators group) to write into any folder on disk C:, including C:Program Files. One day I decided to tu on the UAC in order to play with Windows 8/10 apps. Then, when I have tued off the UAC back, I was surprised that I should be elevated to Administrator in order to have the write access to most regions of disk C:. How to restore my original rights on disk C:?