Computer devices (10) that are resistant to contamination by microbes are provided. The device (such as a keyboard (10), mouse or other computer device) is treated or manufactured with a photosensitizer compound that is activated by electromagnetic radiation (16) to provide an antimicrobial effect. One or more light sources (14; 19) may be utilized to activate the photosensitizer compound and these may be incorporated inside or outside of the computer device (10). A laptop computer in which the electro-magnetic radiation is provided by the display screen (30) so as to provide an antimicrobial effect to the keyboard (13) is described.