Windows 7: Windows Media Player, I require some assistance

Okay, to start off.. I did something stupid. For all .sfk files I chose properties. And thought I could open them and put them to use.. But after I chose a PROGRAM OF ANY KIND to open it. It didn't work. I was like "Dang it.." and tried to open the video itself.. And then it said "Server execution failed" I've done plenty of things. Even restarted the program, setting it to default, and some other stuff. And it worked! .. For a day, and a day only. I tried it recently again, and now it opens for a split second with a white screen, and disappears into the thin air of my computer screen. Any solutions to my problem? (Or any way to set the properties of all my .sfk files back to defaults?)

(Bump, I really need some help, this problem is getting in the way of my hobby which is making movies.)

The way I fixed it was to actually uninstall the program you use to create movies and reinstall it again. If that fails, you will have to be patient and wait for others to respond to the post.