Quadzilla99,
You should've just changed the default player for video files. You can do this by right click on the file in windows(outside of limewire), then click on properties and you can change it from there. This link might help explain it better:
How to set the Default video application
Don't know why they won't play now. It's usually a codec problem.
Try playing it with
VLC media player or
DivX player. These players have the codecs built in and are free. If the files play with these then it was prolly a codec problem.