Find all files that are NOT of a specific type/extension in folder?

Windows 7 Ultimate 64bit:

I'm looking for a way to find all the files in a directory that are NOT of a specific file type or extension.

Example: I'd like to find every file that isn't an .mp3 in my music folder (and all sub folders).

type this in the search box of the directory you want to search

NOT *.mp3

From a command prompt you can pipe the direcotry list into findstr, and use findstr's V switch to exclude lines like the filter (in this case, lines ending in .mp3), as well as the I switch to make the find procedure case-insensitive.

dir | findstr /vi "*.mp3"

I just open the folder with Windows Explorer, add the Type column to the display, and sort on it.