It has not been possible to drag & drop songs from the LW program to iTunes for several LW versions so I'm told. Best way is to use Explore button to access that folder on desktop. Then drag & drop them from there onto iTunes Library icon at top left of iTunes window.

Your file sounds suspicious to me. (best quality) is how some spammers name their files. If you have VLC player try opening with that program. Although it is primarily a video player, it can open most audio files too. So if VLC cannot open it then ... probably not 'real' audio files.
VLC - (click on link) _ (choose nearest mirror site)