Go half way down the page on this site for pictures of opening it and about the hooks holding it together: http://www.tomshardware.com/forum/280978-32-identify-controller-verbatim-case
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Here's a video on disassembly of another drive but it will give you an idea of how these drives are generally opened up: https://www.youtube.com/watch?v=WyV6-MqLUxA
Go half way down the page on this site for pictures of opening it and about the hooks holding it together: http://www.tomshardware.com/forum/280978-32-identify-controller-verbatim-case