David,
As Dave noted, the media stuff may be a dead-end, but in other instances you can use an add-on like 'User Agent Switcher' that will setup the browser ID tags to make it appear as if your OS/2 based FF is actually a Winx, Linux, MAC, whatever you want.
I occasionally use this approach with sites that insist I need a specific level of FF and clearly that is not available on our platform.