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LM317 can be used for regulated dc power supply upto 37V. For more voltage range, a zener can be connected at the reference pin.
7408 is an active componet that need power supply to work otherwise it wont work
IC 7806 is the voltage regulator that gives 6V dc voltage from 230V ac power supply. It is used to give power supply to the IC which operates on 6V.
If it as a 20 or 24 pin connector and a 4 pin connector then it is a ATX power supply.
24 pin connector is required to supply power to the motherboard.