In version 2.79 in video sequencer when I try to add movie that is .wmv I get an error message that it can not be loaded. On earlier version there is no problem adding the .wmv file. is there a addon that needs to be selected? or how to correct this error
I am having the same exact issues with completely normal Theora+Vorbis ogv files that had always been accepted by Blender 2.48. Something is broken in Blender 2.49a, both in the release candidate and the definitive version.
I have (temporarily) solved the issue by installing Blender 2.78a, i.e. the most recent previous version to 2.79. In my case it is easy because 2.78a is simply the version you get at present in the Debian Stretch repositories, but depending on your OS you may want to have a look at https://www.blender.org/download/previous-versions/
Because of comments stating that this should be a comment, not an answer and such, I think I should rephrase my answer as direct answer to your questions, for the ease of readers who might have difficulties with the text I have written so far:
Your direct question number 1:
is there a addon that needs to be selected?
Direct answer: No, it is a bug in version 2.79a
Your direct question number 2:
or how to correct this error
Direct answer: Install the most recent previous version, i.e. Blender 2.78a, to be able to import your .wmv files while hopefully retaining most of the functionality you need in Blender 2.79a.