PC won’t start? 18 proven fixes to revive a computer that won’t boot

Meta description: Computer won’t boot or PC won’t start up? Try these expert fixes for no power, black screen, boot loops, and Windows startup errors—step-by-step.

When your computer won’t boot, it can feel like everything stops. Don’t panic. Most “PC won’t start” issues come down to a few common culprits—power, hardware seating, or corrupted startup files—and many can be fixed at home in minutes. This guide explains why your PC refuses to start and walks you through practical, step-by-step solutions that work for Windows 10/11 desktops and laptops.

At CyReader, we test gear daily—from power supplies to SSDs—so we’ve seen these problems up close. Below you’ll find the exact checks we use in the lab, plus when to escalate to warranty support or data recovery. If you’re on a Mac, see our Mac startup troubleshooting guide instead, but for Windows users, let’s get your system back to life fast.

Quick answer: Start by verifying power (wall outlet, PSU switch, power cable), disconnect all peripherals, and force a cold boot. If you see lights/fans but no display, reseat RAM and GPU, check monitor input, and clear CMOS. If Windows appears but won’t load, boot into the Windows Recovery Environment for Startup Repair, Safe Mode, or System Restore. As a last resort, rebuild the bootloader or reinstall Windows with a bootable USB.

Why your PC won’t start: common causes explained

Power delivery is the foundation. A tripped surge protector, a loose power cable, or a flipped power supply switch can all present as a “dead” PC. Laptop batteries can fail silently, and many USB-C chargers don’t supply enough wattage to boot under load. Even if fans spin, the power supply unit (PSU) might be sagging under startup draw, especially if it’s aged, budget-tier, or paired with a new GPU.

Hardware seating issues are another top offender. RAM that’s slightly out of slot, a GPU that lost contact after a move, or a misrouted motherboard standoff causing a short can all block POST (Power-On Self-Test). Display problems often masquerade as boot failures, too: a monitor on the wrong input, a loose DisplayPort cable, or a dead HDMI port results in a black screen that looks like “no boot.” Beep codes or diagnostic LEDs on the motherboard often point right to the faulty component.

Software can derail startup once firmware hands off to your OS. Windows updates interrupted mid-install, corrupted drivers, malware, or a failing SSD/HDD can cause endless spinning dots, automatic repair loops, or “No boot device” errors. Misconfigured BIOS settings—secure boot toggles, wrong boot order after cloning drives, or an outdated firmware version—can also stop Windows 10/11 from loading. The good news: most of these are fixable without losing data.

Step-by-step fixes when your computer won’t boot

Begin with power and basics. Ensure the power outlet works (test with a lamp), the PSU switch is on (I symbol), and the power cable is seated on both ends; try a different cable if you have one. Disconnect everything except keyboard, mouse, and monitor; remove USB drives and SD cards that could hijack boot order. Hold the power button for 10–15 seconds to fully discharge, then try a “cold boot.” If you hear fans or drives, verify the monitor is on the correct input, reseat the video cable, and test an alternate cable or port. For laptops, try removing the battery (if possible), disconnect AC, hold the power button 30 seconds, then reconnect power only.

Move to hardware checks if there’s still no display or POST. Open the case (safely) and reseat RAM: remove and click modules firmly back into the recommended slots; test one module at a time. Reseat the GPU and connect its PCIe power leads; if your CPU has integrated graphics, remove the GPU and connect the monitor to the motherboard to isolate the issue. Check motherboard diagnostic LEDs/beeps; consult your board manual for codes. Clear CMOS to reset bad BIOS settings by using the clear jumper or removing the coin-cell battery for 5–10 minutes. If the system is dead silent, test a different PSU if available, or paperclip-test the unit carefully (only if you know how); otherwise, consider a known-good PSU from our best PSU roundup.

If Windows starts but fails to load, shift to software recovery. Interrupt boot three times to trigger Windows Recovery Environment (power on, then hold power to force off during the logo; repeat). Choose Startup Repair first. If that fails, use Advanced options > Startup Settings to enter Safe Mode; uninstall recent drivers or updates and run sfc /scannow and chkdsk /f from an elevated Command Prompt. For bootloader errors, use bootrec /fixmbr, /fixboot, /scanos, and /rebuildbcd. Try System Restore or roll back to a previous build if an update broke startup. If the drive is failing, back up immediately using a live USB, then reinstall Windows from a bootable USB created with the Media Creation Tool and a reliable USB flash drive (affiliate link).

Tools and parts you may need

• Known-good power cable and surge protector
• Phillips screwdriver and anti-static strap
• Spare RAM stick and/or PSU (borrow if possible)
• Bootable Windows USB installer and external SSD for backups (consider a fast portable SSD; see our latest reviews)
• Thermal paste (if you reseat the CPU cooler)

Symptom-to-cause quick guide

• Fans spin, lights on, black screen: RAM/GPU seating, monitor input/cable, BIOS setting, CMOS reset needed.
• No lights/fans at all: power cable/outlet/PSU switch, faulty PSU, short due to standoff or cable.
• Spinning dots/boot loop: corrupted update/driver, failing drive, bootloader issue, Secure Boot/TPM setting.
• “No boot device found”: wrong boot order, loose drive cable, dead SSD/HDD, missing EFI partition.

Safety, warranty, and data tips

• If your PC is under warranty, don’t disassemble beyond user-serviceable parts; contact the manufacturer first.
• Always ground yourself before touching components; avoid working on carpet.
• Before major repairs, try to back up data via Safe Mode, WinRE, or a Linux live USB if the disk is still readable.

You don’t need expensive diagnostics to solve most “computer won’t boot” problems—just a methodical checklist. Start with power and peripherals, rule out display gremlins, then isolate hardware and repair Windows startup. If you hit a wall, don’t risk your data: back up with a live USB and consider professional help. For next steps, explore our curated guides and product picks below to prevent the next startup scare.

FAQs

Q: My PC has power (fans/lights) but no display. What should I try first?
A: Reseat RAM and GPU, check the monitor input and cable, try the motherboard video output if your CPU has integrated graphics, and clear CMOS to reset BIOS.

Q: How do I enter Safe Mode if Windows won’t load?
A: Force three failed boots to open Windows Recovery Environment, then choose Troubleshoot > Advanced options > Startup Settings > Restart, and press 4 for Safe Mode.

Q: Will Startup Repair delete my files?
A: No, Startup Repair only targets boot issues. Still, back up data first when possible in case your disk is failing.

Q: What does clearing CMOS do, and is it safe?
A: It resets BIOS settings to defaults, often fixing bad memory timings or boot device order. It’s safe—just reconfigure your XMP/DOCP and boot order afterwards.

Q: I get “No boot device found.” How do I fix it?
A: Check drive cables, set the OS drive as first boot device, repair the bootloader in WinRE (bootrec commands), and test the drive’s health (SMART). Replace if failing.

Q: Can I recover files from a PC that won’t boot?
A: Yes. Use a live USB (Windows PE or Linux) to copy files to an external drive, or move the drive to a working PC or USB enclosure for data access.

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Explore related CyReader guides and picks

• Windows 11 troubleshooting: 25 fixes for common errors
• How to clean install Windows 11 from a bootable USB (step-by-step)
• Best power supplies (PSU) for gaming PCs in 2025
• Top surge protectors and budget UPS units to safeguard your PC
• NVMe SSD buyer’s guide: speed, endurance, and the sweet-spot picks
• Best portable SSDs for fast backups (editor’s choice)
• How to update your BIOS safely (with fail-safe checklist)

Helpful gear

• Reliable USB flash drive for Windows installer (affiliate)
• Gold-rated 650–750W PSU for midrange GPUs (affiliate)
• DisplayPort 1.4 and HDMI 2.1 cables tested for 4K/144Hz (affiliate)

Need personalized help? Drop your exact symptoms (lights, beeps, LED codes, motherboard model) on our forum or tag us on social—we’ll triage your build like we do in the test lab.