i7-2720M Quad Core 2.20Gm6600 precisionm 6600 doesn't see seagate 2tb hybrid hd (part ssd)i put hd in blaq x usb caddy and m6600sees it. that's where I partitioned and formatted it. 2 places to put hd and it no see. it sees and formats other 1/2 tb and 2 250 gb, even install os on them no prob. but won't see seagate.
Check with the manufacturer of the external enclosure - not all of them (particularly older ones) will support a drive that large.