Computer Repair do not want to Boot

At the time the computer is turned on by pressing the power button, so the first time that does work is the BIOS POST (Power 0n Self Test).
BIOS works to know all the devices installed on the motherboard (the computer) while ensuring that all system devices to function properly.

When the BIOS detects a problem during POST, the BIOS will send an error message.
So if your computer will not boot when turned on in advance and should go off all external devices such as printers and so on.


Step Improvement.
1. The first step is to ensure the processor components, memory, video cards, hard disk is installed  correctly.
2. Make sure the component that bersolder no loose or semi loose in the motherboard.
3. Disconnect all the devices that are not mandatory, external devices such as scanners, printers, flash and so on, because if installation is not true will cause the I / O error.
4. Turn on the system and try to plug the existing one by one device to test the source of the problem.
5. Double-check the jumpers on the motherboard.
Make sure the processor type, bus speed and voltage jumpers are installed correctly.
6. Make sure the BIOS jumper is in proper position.
7. Change the BIOS settings to the default position to ensure the problem.
8. Check all cables to the motherboard what is correct.
9. Check whether there are components that are experiencing excessive heat.
If there is, then change it and set the BIOS settings to the lowest.