Work out which one it is
Sit in front of it and watch carefully for thirty seconds.
Nothing at all. No lights, no fan noise, no sound, nothing on screen. Press the power button and the room stays silent.
Something happens, but no picture. Lights come on, you hear a fan spin up or the drive tick, but the screen stays black.
It starts, then doesn’t finish. You see a logo or a spinner, then it restarts, or hangs, or drops to a blue screen and loops.
Each one has a different fix. People often describe all three as “it’s dead”, but the second one in particular often turns out to be a cheap fix.
Nothing at all
Start at the wall and work towards the computer, because the cheapest faults are usually there.
Try a different power point, and a different one on a different wall if you can. Power boards and individual sockets do fail. If the machine plugs into a surge protector, plug it straight into the wall as a test.
Check the power brick itself. Most laptop chargers have a small LED on the brick or the plug. If there’s no light, the charger is the likely problem. A charger is a fraction of a repair bill, and third-party ones for common models are easy to find, though for a laptop you use every day we’d recommend the manufacturer’s own.
On a laptop, try it with the battery out (if it comes out) and the charger in, then the other way around. A battery that has failed short can stop a machine starting even with power connected.
Then drain the residual power. Unplug everything, hold the power button down for a full thirty seconds, then reconnect just the charger and try again. Holding it for the full thirty seconds lets the leftover charge drain from the board, which fixes some faults that a normal restart doesn’t.
On a desktop, check the switch on the back of the power supply. It is a small rocker near the cable socket, marked I and O, and it gets knocked when machines are moved or cleaned behind.
Lights on, screen black
Be patient with this one, because the computer itself is often fine.
Listen first. If fans are spinning and the drive is active, the computer is running and the problem is likely the screen or its connection.
On a desktop, check the monitor before anything else. Is it on? Is the input set to the socket the cable is in? Modern monitors have several inputs and can sit on an empty one showing a black screen. Try the monitor with something else, a laptop or a console, to prove it works.
Check which socket the cable is in at the computer end. Desktops with a separate graphics card have video sockets in two places: the ones on the card, lower down, and the ones on the motherboard itself. Plug into the motherboard when there is a card fitted and you get exactly this symptom.
On a laptop, turn the brightness right up, then plug in an external monitor or a TV with an HDMI cable. If a picture appears on the TV, the computer is fine and the fault is in the laptop’s screen or backlight, which is a specific repair that can be quoted.
It starts, then stops
Repeated restarts and freezes during startup usually mean one of three things: the drive is failing, something changed recently, or it is overheating.
Overheating is usually easy to spot. The machine is hot to touch, the fan is loud before anything has happened, and it gets worse the longer it stays on. Laptops used on beds and couches block their own intakes; years of dust does the same thing to a desktop.
If the problem started right after an update or new software, that’s the most likely cause. Windows will usually offer Startup Repair after a few failed attempts, and letting it try is reasonable.
Stop if you hear clicking. A regular, rhythmic click or a repeated spin-up-and-stop from a mechanical drive means the drive is dying, and every further attempt to start it reduces what can be recovered. Each extra attempt makes recovery harder. Turn it off and leave it off until someone can take the drive out and image it.
When to stop trying
Some symptoms mean put it down and get someone to look:
- A burning or hot-plastic smell
- Clicking, grinding or beeping from the machine itself
- Any liquid involved, at any point, even weeks ago
- Visible swelling — a laptop whose trackpad has lifted or whose case no longer closes flat has a swollen battery, which is a fire risk and needs handling properly rather than charging again
Take liquid seriously. It causes corrosion, which keeps spreading long after everything looks dry, so a machine that seemed fine after a spill can fail weeks later. Switching it on before it has been cleaned can ruin a board that could have been saved.
Before you do anything else, if it does start
If you get it running, even briefly, copy your files off straight away, before any diagnosis or decision about repairs.
Intermittent starting is often the first sign of a drive on the way out, and the gap between “boots most times” and “does not boot at all” can be days. Copying files from a drive that still works is free. Recovering them from one that has stopped working is specialist work, and expensive.
Photos first, then documents, then everything else. Most of what is left can be downloaded or reinstalled.
What it usually turns out to be
In rough order of how often we see them: a failed charger or power brick, a monitor on the wrong input, a failing drive, a swollen battery, and a power supply that has given up. Only two of those are expensive, and a monitor on the wrong input costs nothing to fix. Five minutes of checking can save you a lot of money.
