Desktop Repair

To Repair Desktop Computer First of all to find that which part is faulty....
Mainly there are three things Which can be faulty:-

Motherboard ( include RAM & Processor )

Hard Disk Drive

S.M.P.S ( Power Supply )

If the Computer is dead means doesn't power on then check the power  supply :
How to check Power supply working or not ? :-
Shot the green wire with any black wire as shown below....

If the fan of power supply Starts, it means that the power supply is not faulty.....

If power supply is ok... then check mother board by disconnecting any other device from it if your computer doesn't start ,, it means your mother board is faulty

If it starts correctly then check any other devices connected with your motherboard like hard disk drive ,

dvd writer , sound card , graphics card etc.....