Strange. Hooking up an 8700 to your PC and DM will not remove or uninstall software. It just won't do it. Something else has happened here.
I would recommend rebooting your PC, opening DM again and checking.
Finally, you really don't need the Media Manager. It is a horrible clunky piece of software which causes loads of problems (and questions) for which there is no need. Just enable Mass Storage on you Media card. How do I add media files to my microSD card? - BlackBerryFAQ