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株式会社オブライト
Business DX2026-07-236 min read

Office PC Won't Start or No Internet? A Triage Checklist

A triage checklist for office PCs that won't start and networks that won't connect: 'one person or everyone?' narrows half the causes. Correct router restart order, symptom-based PC steps, stopgap operations, and repair-vs-replace judgment.


Conclusion: 'Is It Just You, or Everyone?' Narrows the Cause in Half

When a PC won't start or the network drops, it's easy to panic — but the first step is simple: check whether the problem is limited to your own desk/PC, or affecting the whole office. If everyone is affected, suspect shared equipment like the internet line or router. If it's just you, the likely cause is your PC itself, a cable, or your Wi-Fi settings. This one check alone saves you from wasted effort, like spending 30 minutes disassembling your PC alone.

Triage Table: 'Can't Connect to the Network'

SituationLikely CauseFirst Step
Entire office can't reach any service (email, web, internal systems)Line outage / router or ONU malfunctionRestart the router/ONU, check your carrier's outage status page
Only your own PC can't connectLoose LAN cable / Wi-Fi settings / network glitch on your PCReseat the cable, reconnect to Wi-Fi, restart the PC
Only one specific service (cloud accounting, a certain site) is downOutage on the service provider's sideCheck that service's official status page or social media
Wired connection works but Wi-Fi doesn'tWi-Fi router signal trouble or congestionRestart the router, test whether other devices can join the same Wi-Fi

How to Properly Restart Your Router and ONU

- ① Unplug the power for both the ONU (line termination device) and the router
- ② Wait 30 seconds to 1 minute before plugging back in — restarting too fast can leave the reboot incomplete
- ③ Power on the ONU first, then the router, and wait 1–2 minutes for each device's lights to settle into their normal pattern
- ④ Only try connecting your PC or phone once the lights show a normal state

Repeatedly power-cycling the equipment out of impatience can actually slow down recovery. Light colors and blink patterns differ by device, so compare them against the 'normal state' described on the unit or in its manual while you wait.

PC Won't Start: Checklist by Symptom

SymptomLikely CauseWhat to Do
No response to the power button, no lights at allBad power cable/power strip, or internal power supply failureTry a different cable or outlet
Powers on but the screen shows nothingLoose monitor cable, or a graphics-related issueReseat the cable, check the monitor's power and input source
Stuck on a logo or loading screenOS problem or storage (SSD/HDD) issueIf it doesn't change after ~10 minutes, don't force a shutdown — note the symptoms and consult someone knowledgeable
Unusual noise (clicking, whining, etc.)Possible physical hard drive failurePower off and stop repeating restarts or leaving it powered on

- Don't keep a noisy hard drive powered on — it lowers the chance of data recovery
- Don't disassemble the PC or unplug/replug components without knowing what you're doing
- Don't repeatedly force-restart the PC hoping it "might fix itself"
- Don't change passwords or security settings on your own judgment

Keeping the Business Running While It's Down

If repair or recovery looks like it will take a while, the first priority is deciding what will stand in for the affected work. For a line outage, using a smartphone's tethering feature to keep minimal email and cloud access running, or sharing a single 4G/5G mobile router across the office, are effective stopgaps. Deciding in advance how to keep operating when systems go down is the idea behind business continuity planning (BCP). See IT-BCP Basics for Small Businesses to prepare for this ahead of time, so you can respond calmly the next time something breaks.

Repair or Replace: A Rule of Thumb

FactorFavors RepairFavors Replacement
Age of the PCUnder 3 years5+ years (parts may be discontinued)
SymptomA single failed part (power supply, memory, etc.)Physical storage failure, or multiple issues at once
Repair estimateUnder half the cost of a new PCOver half the cost of a new PC
Business impactA spare machine can cover the gapWork stops immediately with no easy substitute

Don't Carry the Burden Alone

Many small businesses have effectively one person handling IT, or someone juggling it alongside other duties. Making every decision alone during every incident leads to slower response and real personal strain. Keep a ready list of who to call — repair vendors, maintenance contracts, anyone you can consult — prepared in advance, before the next problem hits. For more on building this kind of support system, see A Survival Guide for the Solo IT Person.

Frequently Asked Questions

The power light is on but the screen stays black. Is the PC broken?

Not necessarily. Common simple causes include the monitor itself not being powered on, the wrong input source selected (HDMI/DisplayPort, etc.), or a loose cable. Start by checking the monitor's own power and input settings.

Besides restarting the router, is there anything else I can check myself for a network problem?

Make sure the LAN cable is fully seated, or if you're on Wi-Fi, that you're connected to the correct network name (SSID). Testing whether another PC or phone can join the same network also helps tell whether the issue is your device or the connection itself.

How urgently should I deal with a PC making strange noises?

Noise from a hard drive is often a sign of physical failure, and the longer you keep using it, the higher the risk that data becomes unreadable. If important data is on it, power the machine off right away, avoid further use, and consult a specialist.

Who should we ask if no one in the office really knows IT?

Your main options are the PC manufacturer's support line, the retailer you bought it from, or a local IT maintenance provider. Deciding in advance on one maintenance contact you can call in an emergency saves a lot of stress when something actually breaks.

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