you should be aware that a removeable rack requires at least 2 computer desktops to have this rack installed, otherwise you could remove the hard disk and store it in a safe vault. not really useful.
an external drive enclosure is something completely different. it is a box that you can put any IDE drive into it like cd-rom or hard disk. they use either USB or firewire and you can just plug them into any computer. you don't need to install any hardware into each computer. this may be what you really wanted.
here are some: