In a control apparatus for use in a multiple light projection type image display apparatus, the control apparatus includes a light source driver part configured to drive a plurality of light sources; and an apparatus controller configured to control the light source driver part. In a hard disk drive, a piece of sector data to be written or read is pre-associated with a sector number of a sector where the piece of sector data is to be written or read. Modular units can be united in an assembly, and at least some of the modular units have a switching system to selectively transmit andor receive one or more of power, thermal and data transmissions. An execution of the scheduler software module by the DSP implements one of a various modes of an interrupt request routine. The slidable mounting plate allows the adjustable keyboard tray to move in a lateral direction substantially perpendicular to the bracketing mechanism for repositioning the adjustable keyboard tray with respect to the horizontal surface.