I just took the lid of a amstrad dx890 and inside was a seagate 500gb hdpipeline 2 inside. I have used in my vu+ ultimo and working well so hopefully you have one of them or if you have the new type of sky hd box it should be a 1tb hdd
Open the single screw holding plastic chassis. Prize 3 clips of plastic chassis slightly and then push plastic forward. 2 screws hold buttons. 3 screws on side for metal cover.