renaming files

[Brian]

I do not know when it happened, but I suddenly cannot
rename avi or mpeg files without them becomeing unusable
now. A month ago I went through and renamed files with
no problem and now when I do it I get an "If you change a
file name extension, the file may become unusable. Do
you want to change it?" If I click yes, the icon changes
and the only way to play the file is go into "Open
with..." and choose windows media.
Thanks

 

[Pokey]

Well, just change the name of the file and not the extension.

 

[Brian]

I don't know how. I am not doing anything different now
than I was before. All I do is right click and rename.
When I hit enter, I get that message.
Thanks