OK, I was just asking to make sure you weren't running as a general user
with that turned off, you wouldn't change Administrator within WD, but it
makes a difference in how WD runs if these settings are not correct.
How about taking a look at your Control Panel > Admin Tools > Event Viewer
System > View > Filter on WinDefend
and see if there are any errors or warnings around the time that scan ends.
Another option is to try a repair in Control Panel > Add/Remove > Click
here for support then > Repair
But I see your running an older version of the program, so I'd be tempted
to first go to the WD website and download the current Version which is:
Windows Defender Version: 1.1.1347.0
It doesn't yet update the program version through the update function
within the program, just engine and definition versions.