Abstract: A mechanism for mounting and removing a data storage device, such as detachable hard disk or optical disc driver, into and from a computer according to the present invention includes a lever pivotally mounted in the middle front of the data storage device; an engaging portion formed on one end of the lever; and a guiding rail formed on a carrier to be engaged with the engaging portion of the lever. The guiding rail is so designed to transform the movements of the lever into assistant forces of pushing and pulling the data storage device into and from the carrier. Moreover, the engagement of the lever to the guiding rail restricts the moving speed of the data storage device and prevents it from being bumped or damaged.