Now plug in a keyboard, mouse and monitor, and turn the PC on. Don't attach the case covers back on yet, because it's important to check that the processor fan is spinning. If it's not, or if there are any worrying sounds or smells, turn the PC off immediately and check that every component is correctly inserted in its place and that each central component is connected to the PSU. A PC may make a single beep when turned on to inform of its good health. Multiple beeps or a long tone may suggest a component hasn't been properly connected. When the PC first powers up, enter the Bios. This is achieved by pressing a key when starting the computer - typically F2 or Delete. There will be a page, usually called 'PC Health/Status', which shows the processor and case temperature. Intel recommends a temperature under 100°C for its modern Core 2 Duo processors, but anything above 70°C when initially turned on isn't healthy and probably means that the cooler hasn't been attached properly. Modern processors should ideally measure between 20°C and 50°C when starting from cold.