10

It would help us, i.e. finding "undesired files" to delete.
In search box if I type "*.mp3" it will show all files terminated in .mp3. ok
But if I want to delete the files non mp3 from the path?

This is the idea: use special signs to advanced search, like Google
I would type "! *.mp3" or "no *.mp3" or "*.mp3" and check an "Inverse search" chechbox somewhere in the dialog.

Also it has other signs to enhance the search:

no - returns the files that don't match the expression
"no *.mp3"
and - returns the files that match the two or more expressions
"*.mp3 and *.ogg"

"no (*.mp3 and *.ogg)" - returns all files not ending with mp3 or ogg