File extensions. How to find which software runs this file extension?

This is a riddle which is sometimes difficult to crack.
Why does Windoze have file extensions?
Because the designers intended it to..really?
Let's not get into that..That's a windows (actually DOS)design question.
Anyways,You'll find what you're looking for:
The answer to the question that the subject of the post asks..
at a rather cute site called www.filext.com
Here is the query for which I searched.Apparently my Olympus digital cam gives me movies which only Apple QuickTime can play.I thought .mov had something to do with an open file format, honestly!
Well then..Go check out the site.I found the utility of the site rather nice!
Cheers,
Narayan