yes, but it won't be external. unless it's some kind of weird thing i've never seen before, the 'external' part means it's for a floppy. but an internal hard drive will fit in it just like any other 3.5" bay.
i still think the best thing for you is a normal external, but you really haven't said what your needs for it are. just plain old additional storage? internal is fine. a more portable storage container that can be swapped between computers if need be? external drive. i'd only recommend spending the extra money on an external dock/enclosure plus an internal drive if you need functionality like what nuke was describing he used his for. or you're REALLY dead set on having a top end drive in your enclosure. that scorpio black is likely (slightly) faster than what would come in an external drive, but they don't like disclosing what actual drive is in those, so you can't really be sure. but like someone else pointed out earlier in the thread, externals usually don't need the tiny bit of extra speed. you're not constantly accessing them, and backups are going to take forever even on the slightly faster drive anyway.