The IE tab add-on will do this. You can get it here - https://addons.mozilla.org/en-US/firefox/addon/ie-tab-2-ff-36/

For more about add-ons, see Find and install add-ons to add features to Firefox

Since IE Tab is actually your computer's current version of IE displayed inside a Firefox tab, you may want to limit your use of it to trusted sites given recent news.

Problem with this IE Tab is it so outdated. We are on FireFox version 29 now. IE tab was good for version 3.6, but we need something newer now.

Additionally, I don't want to simply 'run IE in Firefox', I want to emulate the programming that works with ActiveX to replace IE on my computer. Like jscher2000 said, IE isn't looking very good right now.

There are several different IE Tab extensions. I lost track of the relationship/derivation some time ago.

ActiveX controls are a technology from the 90s. Sites using them know full well that they don't work in non-Microsoft browsers. If they don't build-in an alternative, you're stuck.

Thatt just stinks jscher2000! MS should make their sites more compatible with browsers other than their own, especially seeing how out of favor their browser is falling. I was hoping someone else knew more on this subject than me, but looks like my fear is true... If I want it fixed I am going to have to code it myself.

I don't use Sharepoint, but if the UNC path is exposed in the page as a hyperlink, or if it opens in a Firefox tab as a file:// URL, there might be a Firefox extension that can launch it in Windows Explorer instead.