I downloaded and installed J River media center for evaluation. It is not what I am looking for so I uninstalled it right away. Now all the video files on my computer says mediacenter.12.file. I used DVDFab Platinum to copy those .
How can I get rid of this file type and change them back to what it was before?

Try using Restore to take your system back to the day before you installed that ill mannered software. There may be an easy way to change all the file associations that it hijacked at once, but I don’t know it.

I will do that, thanks a lot.