A disk drive unit having a disk loading mechanism, for use in a mobile device. The loading mechanism is arranged for receiving a disk (A) through an opening in a housing of the device and bringing it into engagement with the disk drive, and vice versa. It comprises a tray (8) which is movable with respect to the housing and the disk drive between a first position for receiving a disk and a second position covering the opening and allowing the disk drive to engage the disk. The tray is rotatable about an axis (10) which substantially coincides with the drive axis (11) when in its driving position. This arrangement results in a slot loader having a tray which will hardly project outside the housing, resulting in a robust loading mechanism.