Instruct: Classify an Amazon review into positive or negative sentiment.
Query: beware: defective blu ray disk sold by amazon

the blu ray 2 disk set i just received from amazon is defective. the slection screen plays ok, but when 'play movie' is selected, just the sound plays - the screen is black. i listened for several minutes, thinking it might be some artsy music-only opening, but after 4 minutes i still didn't have a picture.