Take 3 screws out, and pull the caddy with the hd out->slowly to the front - NOT to high and remove the grey cable (there are parts mounted that can get lost on the keyboard body).
take it with a mini-usb cable to you computer and check it there!
If you take a new HD for T4 don't forget to format INSIDE the T4, because of generating the structure for audio recording ...
greetings
frank