Computer maintenance is the practice of keeping computers in a good state of repair. Computer valeting is the in-depth cleaning of the physical components of a personal computer. Usually performed by a computer repair technician, this service addresses the different ways that dirt builds up on four main components: the keyboard, the monitor, the mouse, and the tower/desktop unit. Computer cleaning involves physically cleaning the interior and exterior of a computer, including the removal of dust and debris from cooling fans, power supplies, and other hardware components. This should be after certain period of time (weekly/monthly). A computer containing accumulated dust and debris may not run properly.