from http://bugs.musicbrainz.org/ticket/2310

please add a button to the toolbar that deletes a selected track from your hdd.

This would be especially useful for getting rid of error files for good.

one comment:

Yes, that would be nice. Please make sure it can be used for folders as well. Also, I think it will be convenient to have it in right click context menu for the file browser. It currently only contains refresh, so it won't bloat that menu too much IMO.

Someone linked to a patch at http://garyvdm.googlepages.com/delete.patch
Someone else pointed out a plugin on http://forums.musicbrainz.org/viewtopic.php?pid=6947#p6947