This is normally due to system policies. Easiest method of fixing the issue is as follows, open command prompt in admin mode:
Type in at prompts...
C:\Windows\system32>diskpart Microsoft DiskPart version 6.3.9600 Copyright © 1999-2013 Microsoft Corporation. On computer: WIN81
DISKPART> automount Automatic mounting of new volumes enabled. DISKPART> automount disable Automatic mounting of new volumes disabled. DISKPART> exit
Another option would be to use the windows manager software from yamicsoft for your version of windows, and repair the setting. I do not remember the location however.