All that is happening here is that you have Nero CD/DVD Recording software installed and your default Video Player is Showtime. If you change your default Video Player to Media Player the files will show a different Icon and list of the Default Videos Player but nothing else will change.
You can still play these files in whatever Application you chose without a problem but if you open the Folder that they are in and click on them Nero Showtime will open and play them.
So in answer to your questions
[i]Can I recover the original file?[/i]
You don't need to all that has changed here is the player that they default to.
[i]Is this some sort of malware?[/i]
No it's not anything at all. Don't concern yourself over this.
[i]What can I do about this?[/i]
If you don't like the way that these are displayed remove Nero or change the Default Video Player to something else.
Col