The internal components of the computer are sensitive to electrostatic discharge (ESD). Damage to the motherboard, memory modules, and peripheral cards can occur if these parts are exposed to ESD. If you are familiar with and have a grounding strap, use it while handling any internal components. If you do not have a grounding strap, it is a good idea to touch the computer case anywhere on the bare metal prior to disconnecting the power cord.

Things to Confirm

1. Make sure the power cord is firmly connected to the computer and the wall outlet.
   If the computer is plugged into a surge suppressor, extension cord, or an uninterruptible power supply (UPS) bypass these devices for testing purposes by plugging the computer power cord directly into a wall outlet.
   Surge suppressors can fail or they can have a built-in circuit breaker that may need to be reset. Backup power sources like UPS devices can fail also. Extension cords can introduce poor or inconsistent connectivity because of loose or worn connectors.
   Note: Reinstall the surge suppressor after the problem has been found or after it has been confirmed that the device is working properly.
2. Check for wall outlet power.
   Confirm that the wall outlet actually has power to it. Another device such as a lamp can be plugged into the outlet to confirm power is present.
   Some wall outlets are connected to a wall switch and power can be turned off inadvertently.
3. Check the voltage setting on the power supply.
   On the back of the power supply confirm that the voltage switch setting is in the correct position. Computers used in the United States need to be set to 115v. Computers used in some European countries need to be set to 230v. If the switch is in the wrong position, unplug the power cord, and then move the switch to the correct setting.
   Not all power supplies have a manual switch for this setting. Some power supplies have "auto range" circuitry which automatically sets the power supply for the appropriate input voltage.
4. Check the display device.
   Confirm that the monitor or LCD has power. Turn the display device off and on, and then look for indications that it is functioning properly.
   Often a monitor or LCD displays a message when it is turned on that it does not have a signal. This is an indicator that the display is working and the problem may be the computer and not the display.

Things to Try

1. Replace the power cord.
   Make sure the computer is turned off. Disconnect the power cord and replace it with a different one. Sometimes the monitor power cord is similar and will work for this experiment. If the connectors aren't identical do not force any connections. With a different power cord, press the power button and observe the computer to see if it is booting up. If it seems to be starting, power the computer off and locate a permanent power cord replacement. Discard the old power cord.
   Power cords do not malfunction often. If one has been proven to be faulty, replacements can be easily obtained.
2. Disconnect power and hold the power button for 10 to 15 seconds.
   Make sure the computer is turned off and the power cord is unplugged. Disconnect everything except the monitor and the keyboard. Hold the power button in for 10 to 15 seconds to dissipate any stored charge. Plug power back into the computer and press the power button. Check the front panel LEDs (lights) found on the bezel (front face) or on the optical drives. Check the power supply fan. If the LEDs are on or the power supply fan starts spinning, watch for the boot screen to come up on the monitor. If the computer begins to boot, turn it off and reconnect any external devices. Turn the computer back on and confirm that it boots up.
   This procedure might help the computer to restart if it were shut down improperly. The process drains stored electrical energy that is held in some critical circuits on the motherboard. These circuits are responsible for starting the computer properly. This is not a common occurrence but if these procedures get the computer to restart, the computer should function properly in the future.
3. Removing external devices.
   Make sure the computer is powered off. Disconnect everything except the monitor including the keyboard and the mouse. Plug power into the computer and press the power button. Check the front panel LEDs (lights) found on the bezel (front face) or on the optical drives. Check the power supply fan. If the LEDs are on or the power supply fan starts spinning, watch for the boot screen to come up on the monitor. If the computer begins to boot, turn it off and plug in the keyboard and the mouse. Turn the computer back on and confirm that it boots up.
   If the computer turns on, one of the devices previously plugged into the computer may have been preventing the computer from booting up properly. Each device can be reconnected one at a time. Make sure the computer is powered down prior to plugging in each device. If the computer fails to start after a device is reconnected, this device may be causing problems with the computer. Contact the manufacturer of that device for possible resolutions.
4. Use the power supply test switch (older computers only).
   Refer to the product page for the power supply you are troubleshooting to see if the power supply has a "self test" feature. It is normally listed as a test switch. This is only found on some older computers. Follow the test procedures on the power supply component page to complete the power supply self test.
   Some older computers were equipped with a "self test" circuit. If the procedures are followed closely when testing a power supply with the self test feature, an accurate diagnosis of the power supply can be quickly made.
5. Check the power switch header.
   Make sure the computer is turned off. Disconnect all external devices except the keyboard and the monitor. Position the computer where it cannot fall and can be easily opened and accessed. Remove the cover and locate the front panel LED and power switch connector. Remove the connector from the header and reinstall it. Confirm that the power cord is connected properly and press the power button. Observe the computer to see if it is starting properly.
   If the computer has recently been opened for service or upgrades, it is possible that the power connector was been seated properly to the motherboard power header. In most cases this is a "keyed" connector and can be connected properly in only one way. However, if not carefully reconnected, it is possible to offset the connector to one side and cause an improper connection preventing the computer from starting normally.
6. Reconnect main motherboard power connector.
   Make sure the computer is turned off. Disconnect all external devices except the keyboard and the monitor. Position the computer where it cannot fall and can be easily opened and accessed. Remove the cover and locate the main power connector. This connector is the main power supplying the motherboard from the power supply. It is the largest of the power supply connectors. Remove the connector from the motherboard and reconnect it. Make sure the connector is completely seated and firmly connected to the motherboard.
   This connector has a retention clip that must be pushed in before the connector can be removed. Sometimes it can be difficult. The objective is to ensure that the motherboard has a solid and complete connection to the power supply.
7. Unplug internal drives.
   Make sure the computer is turned off. Disconnect all external devices except the keyboard and the monitor. Position the computer where it cannot fall and can be easily opened and accessed. Remove the cover and locate the internal drives. Unplug the power and data cables from all the drives. Connect power cord and monitor to the computer and press the power button. If the computer starts and begins to boot, turn it off and reconnect each drive one at a time. Make sure the computer is off before connecting each drive.
   If the computer fails to start after connecting a particular drive, the drive may be damaged and should be replaced. If the computer begins to start successfully when the drives are unplugged, one of the drives may have a short circuit or internal electrical problem that is preventing the computer from starting properly. If there is a second desktop computer available, try the drive in the second computer. The second computer should have similar, if not the exact symptoms, when the bad drive is installed.
8. Ensure the peripheral cards are seated.
   Make sure the computer is turned off. Disconnect all external devices except the keyboard and the monitor. Position the computer where it cannot fall and can be easily opened and accessed. Remove the cover and locate the internal peripheral cards. Press down evenly on all the peripheral cards. This should ensure that the cards are firmly and evenly seated within their slots. Perform this on each card in the computer. Ensure that the keyboard, monitor, and the power cord are connected. Press the power button and observe the computer and the display. If the computer seems to be starting properly, turn it off and reconnect all devices and replace the cover. If the computer does not start properly make sure it is off and remove all the peripheral cards. Press the power button and observe the computer to see if it seems to start. If it does, turn the computer off and replace the peripheral cards one at a time. Do not remove or add cards when the computer is on. If the computer fails to start after a particular card is installed, that card may be causing the computer to fail. If all cards have been replaced and the computer is now functioning properly, the process of removing and reinstalling the cards may have addressed the problem. Replace the cover and reconnect all devices.
   It is possible for peripheral cards to become unseated while moving the computer or during the shipping process. If the computer has been recently opened and cards had been removed and replaced, a card might not be fully or properly seated in its slot. If the computer begins to function normally after a new or existing peripheral card has been removed, it is possible that the peripheral card has recently suffered electrical damage of some kind and is preventing the computer from starting properly. Even new peripheral cards can be faulty or damaged.
9. Reseat the computer memory.
   Make sure the computer is turned off. Disconnect all external devices except the keyboard and the monitor. Position the computer where it cannot fall and can be easily opened and accessed. Remove the cover and locate the computer memory. Remove the memory from each slot. Press the power button and observe the computer. Listen for error beep codes (a series of beeps heard from the motherboard indicates there is a problem). If the computer seems to start or error beeps can be heard, turn it off and replace the memory modules one at a time. Make sure the computer is off whenever adding or removing modules. With a single module installed, press the power button and observe the computers behavior. If the computer seems to start normally, turn the computer off and install the remaining memory modules one at a time. After each module is reinstalled, turn the computer on and confirm that the computer is still starting normally. If a memory module is installed and the computer stops starting normally, that memory module may be preventing the computer from starting normally.
   The internal components of the computer are sensitive to ESD (electro static discharge). Damage to the motherboard, memory modules, and peripheral cards can occur if these parts are exposed to ESD. Memory does not often go bad if left alone. When it does fail, error beep codes can usually be heard coming from the motherboard. If the memory had been handled recently without proper ESD grounding it could have been damaged by ESD and will need to be replaced. If new memory has recently been added, remove the new memory and see if the computer starts and runs normally without the new memory installed. Be sure to point out that the modules should never be forced into their slots. Observe the module very closely to make sure it is aligned properly during replacement.