Install and Replace SMPS
Installing the SMPS --
The power supply of your PC is controlled by SMPS or power supply unit. When it got damaged your system fails to start, your desktop PC can exhibit any number of strange behaviors. If your PC is suffering from seemingly random reboots or doesn't start at all, the power supply unit (PSU) might be damaged.
If you are replacing a SMPS first thing you have to do is to unplug all wires and cables attached to CPU. Now start with laying down your CPU on its side with its side panel removed, and the motherboard facing up.Gently place the new unit inside the case so that its screw holes line up with the holes in the case. The connection for the AC power cord should be facing to the outside of the case. Now fix it with screws. Here is a checklist of connections:
1. One (1) 20/24-pin main connector(Motheroard)
2. One (1) 4/8-pin ATX12V connector
3. Any required hard drives or optical drive connector(s)
4. 6/8-pin PCI Express video card power connector(s)
Each connector type is designed to prevent it from being improperly inserted, so it's really hard to go wrong here. First insert 24 pin connector in motheroard. For hard drives and CD drives, use the larger 4-pin auxiliary connectors for IDE drives and Serial ATA power connectors for Serial ATA drives, but do not plug both types into one device. Use 6\8 pin connector for video cards.
Following these steps, you should be able to install a power supply in most standard cases.
Replacing the SMPS --
The process for replacing the SMPS is same as installing the new SMPS with an addition of shutting down the computer and unscrewing the screws of old SMPS along with removing all SMPS cables and connections in the cabinet or chassis.