is this a DVD-Drive or a stand alone player?
if this is an ODD then use something small like a hair pin and insert it into the small hole just under the tray.
edit// never mind i should read the Title more clearly. sorry.
might try unplugging it for a minute then press and hold the eject button just after pluging it back in. this way the tray will open before the player is trying to read the disc. if not then will probably have to take the cover off.