Not sure what could be going on since the drive and enclosure seems to work fine on a laptop with XP, I would suspect that perhaps either the drive or the enclosure electronics might require a firmware update to make them compatable with windows 7.
Have you tried inserting a music CD into the drive, leave it connected and turned on and then rebooting the laptop rather than bring the DVD on line when the Laptop is already running. Also make sure that the laptop has the most current drivers available from Toshiba, especially chipset drivers and you may even want to look for a more current BIOS update from them than the one you are currently running.