Using 3 or more hard disks will require at least 230 Watts PSU otherwise the system may not have sufficient power to run . Two different types of keyboard which is one that is membrane keyboard and the other is the clicking keyboard. Microsoft Natural Keyboard seems to be one of the best keyboard I have experienced. Microsoft Mouse and the Logitec Trackball Mouse seem to be the best I have come across. There are laser, dot matrix, deskjet, bubblejet and line printers.
Laser printer is used for printing legal documents and normally used in office.
Dot Matrix will be used for those who need to print carbon copies. Deskjet and Bubblejet are low cost color printing. Line printer is used for fast printing in office. Scanner Scanners now come with A4 or photo type. It is a means of getting your document or picture into the computer for editing.