Unable to install plugins

Question

Plugins are downloaded several times but not being installed

Answer 1

Note the light blue text in the posts are clickable links and will in this instance lead to support articles with further information. Obviously I do not know what security software you use, but by default you probably have a Windows firewall if nothing else.
1) see the linked article in my last post, specifically look at:
*https://support.mozilla.com/en-US/kb/Software%20Update%20Failed#w_run-as-administrator
2) What security related software is in use on your system ? eg
* firewalls
* Security suites & Anti Virus programs
*other miscellaneous addblockers, anti spyware, malware checkers, parental controls etc
It may help to know exactly what it is that you have downloaded and are trying to install.
P.S. <br />
The system with solved vs helpful post is none intuitive and confusing.
If as the 'Owner' you are send in and mark a post as helpful it marks the thread as solved, although obviously this is not as yet.
Conversely many other threads get marked only as helpful, when in fact they are obviously solved. Hopefully this is going to be sorted out, it is something that Mozilla is aware of.