EET owners: Your kit has this bit. No purchase needed.

If the drive is difficult to open and you are opening it to put the drive into a later Xbox 360 with no intention to preserve the enclosure, a screwdriver or pry tool can help.

If you are opening it to replace the drive inside for an original console, it is best to use a plastic pry tool instead. While a screwdriver "works" it will likely mar the enclosure.