I know this is an old post.
If people are still struggling to add the microsoft loopback adaptor, This method works for x64 and x86 versions of the operating systems, open device manager, select network category and choose action -> add legacy hardware. from there select the advanced method to install the adaptor. you will be given a list of hardware categories, select all hardware, and from the list select microsoft -> microsoft loopback adaptor.
select next, next and finish... and the adaptor will be installed.
(this is good for windows 7 and windows 2008/r2