The Computer Will Not Start:
Step-by-step diagnosis

First classify your symptom

Go straight to whichever of the four scenarios below matches yours. Time spent in the wrong section delays the diagnosis.

A — No response at all

In this situation the problem is almost always on the power path. Start with the simplest step; some of the devices brought to our service are resolved at these stages.

• Check the socket and the cable. Does another device work in the same socket? Is the switch on the extension lead turned on? Replace the cable with one that is known to work.
• On a desktop, the 0/1 switch on the back of the case check. If the power supply's own switch is off, there is no response at all.
• On a laptop, check the adapter light. If the adapter light does not come on, the adapter is the suspect; if it does come on but the device does not respond, the charging socket or the motherboard side is suspect.
• Disconnect the battery. On laptops with a removable battery, take the battery out and try with the adapter only. A swollen or dead battery can prevent start-up.
• Discharge the residual power. Unplug the mains lead, remove the battery on a laptop, hold the power button down for 20-30 seconds, then reconnect and try again. This simple step works surprisingly often.

B — The fan spins, there is no image

This is the most frequent picture, and the good news is this: a significant part of the cause is cheap and simple.

First rule out the monitor

Is the monitor's power light on? Does the on-screen menu open when you press the menu button? If it does, the monitor is sound. Then the correct input source make sure you have selected — if the cable is plugged into HDMI 1 while the monitor is set to HDMI 2, you will see a black screen. Try a different cable and, if possible, a different screen.

Pay attention to the graphics card output

On a desktop with a separate graphics card, the cable the motherboard's output is a classic mistake. In systems with a graphics card, the cable must be connected to the card's own output.

Reseat the RAM and the cards

The most frequent hardware cause of this situation is poor contact of the memory. Unplug the device, open the case, remove the RAM modules and refit them firmly into the slots (until the clips seat). Try with a single module and in different slots. Do the same for the graphics card.

Listen to the beeps and watch the lights

Many motherboards report the problem at startup with beep codes or with the status LEDs on the board. Intermittent beeps usually indicate memory; a different pattern indicates a graphics card problem. The manual for your motherboard model states what these codes correspond to; it shortens the diagnosis considerably.

C — Powers on and off

If the system tries to start and then gives up, what is stepping in is usually a protection mechanism.

• Cooler contact: If the processor cooler has come loose or the fan cable is not connected, the system shuts down within seconds. This is the most common mistake after work inside the case.
• Insufficient power supply: If a new and powerful graphics card has been fitted, the existing power supply may not be able to cover the sudden power draw. The correct wattage calculation in our power supply guide we explained.
• Short circuit: A screw that has come loose inside the case, or a standoff that fixes the motherboard to the case incorrectly, causes a short circuit. Taking the motherboard out of the case and testing it on an insulating surface isolates this.
• Dust and overheating: Heatsink blocks clogged with dust can cause the device to shut down before it even has a chance to warm up.

D — It powers on but Windows does not load

If you have got this far, most of the hardware is working; the problem is concentrated in the system drive or the operating system.

• Does the BIOS see the drive? At start-up, enter the BIOS/UEFI screen and check whether the drive is listed. If it does not appear, there is either a cable contact problem or a drive fault.
• The boot order may have changed. Because of a connected USB stick, the system may try to boot from the wrong device. Remove all USB devices and try again.
• Use the recovery media. After repeated failed start-ups Windows automatically offers recovery options; start-up repair can correct damaged boot records.
• INACCESSIBLE_BOOT_DEVICE if you are seeing an error such as this in our blue screen guide go to the disk steps.

In cases where the disk runs noisily, clicks, or disappears and reappears in the BIOS, stop making attempts. These symptoms show that the disk has been physically damaged, and every attempt to power it up reduces the recoverable data.

Prepare the device before bringing it in for service

To speed up the diagnosis, note the following: the make and model of the device, when the problem started and what it started after, the error text shown on the screen, the sounds you hear and what you have already tried. This information saves the first half hour outright on a device brought in to the service centre.

At our service centre in Çankaya we first measure the power path on devices that do not start, and then verify the components one by one with test hardware. When the data on your device is the priority, we apply as standard a backup of the drive before any intervention.