When a computer starts but won’t boot, follow a staged checklist that moves from simple power and display checks to disk and system repairs.
Your PC powers on. Fans spin. Lights blink. Then nothing. No Windows logo. No login screen. A blank panel or a looping spinner is common. Most boot stops trace back to a short list: power delivery, display path, boot device, firmware settings, or damaged system files. This guide gives you a clean order of operations. Start with the items that take seconds and move to deeper fixes only if needed.
Fast Triage: What You See Tells You Where To Start
Match the symptom to the first move. Keep notes as you go. One change per test. That way you know what worked and you avoid stacking new problems.
Photograph each screen and cable layout before changes; pictures help you reverse a step that misfires later.
| Symptom | Likely Cause | First Step |
|---|---|---|
| Power lights on, screen black | Display path or RAM | Test with external monitor; reseat memory |
| Logo loop or “Preparing Automatic Repair” loop | Damaged boot files | Run Windows Startup Repair |
| “No boot device” or “Insert media” | Drive or boot order | Check cables; confirm boot order in firmware |
| Beeps or flashing caps-lock codes | Hardware fault | Check manual for code map; test RAM and drive |
| Mac chime, then spinning globe | Internet Recovery | Use Command-R or Option-Command-R |
Computer Starts But Won’t Boot: Quick Fix Order
Step 1: Rule Out Display And Peripherals
Confirm the panel is alive. Raise brightness. Toggle the display key on laptops. Attach an external monitor. If the external screen works, you’re looking at a panel, cable, or GPU path issue. Next, pull everything that isn’t needed to boot: USB hubs, external drives, SD cards, printers. Leave keyboard, mouse, and power. A stray thumb drive can steal boot priority on many boards.
Step 2: Cold Reset And Reseat
Shut down fully. Unplug power. On a laptop, hold the power button for 15 seconds to clear flea power. Open the case only if you’re comfortable. Reseat memory sticks and the boot drive. If you have two RAM sticks, try one at a time in the recommended slots. Listen for the fan ramp and any beep codes on power up.
Step 3: Check Boot Order And Firmware Basics
Enter the firmware menu with Del, F2, F10, or the maker’s key. Confirm that the intended drive appears first in the boot list. Turn off legacy USB boot entries you don’t need. Save, then retest. If you made changes earlier, load setup defaults, save, and try again. Keep changes minimal and logged in your notes.
Step 4: Try Windows Startup Repair Or Safe Mode
Windows includes tools that can fix common boot stops. Use Windows RE and run Startup Repair. If you can’t reach the desktop, open Startup Settings and launch Safe Mode to remove a driver, undo a bad update, or run a cleaner uninstall. If Safe Mode works, that points to software, not hardware.
Step 5: Test The Drive And File System
Open a recovery command prompt and run chkdsk on the system volume. Many stalls trace back to a dirty file system after a crash or power loss. If the drive throws SMART errors or makes new clicks, back up first with a rescue USB and plan for a replacement drive after you salvage data.
Step 6: Restore, Reset, Or Reinstall
When repairs fail, roll back with System Restore, then test. If that’s not an option, use Reset this PC to keep files or wipe everything. A clean install is a last resort, yet it removes leftover drivers and patch debris in one go. Always back up first.
Proof-Backed Steps You Can Trust
Startup Repair runs from Windows RE and targets boot files. Safe Mode trims drivers and services to a bare set so you can remove the item that blocks normal load. Apple offers a similar recovery layer on Intel Macs with Command-R and on Apple silicon with the power-button hold method. Both platforms let you choose a startup disk and reach a browser for downloads.
How To Open Windows Startup Repair
If Windows won’t load, power on, then interrupt the boot three times with a hold of the power button to trigger recovery. Pick Troubleshoot > Advanced options > Startup Repair. On working systems, open Settings > System > Recovery > Advanced startup > Restart now, then the same path. The page linked above walks through each screen and the prompts you’ll see.
How To Enter Startup Settings For Safe Mode
From Windows RE, choose Troubleshoot > Advanced options > Startup Settings > Restart. After the reboot, press 4 for Safe Mode or 5 for Safe Mode with Networking. BitLocker prompts will appear on encrypted devices. Keep the recovery key handy before you start.
How To Reach macOS Recovery
On Intel models, press Command-R during power on to enter macOS Recovery. On some networks, Option-Command-R starts Internet Recovery and fetches a different installer. From there you can run Disk Utility, reinstall macOS, or choose a startup disk. Apple lists the exact key map on its startup key combinations page.
Root Causes: Hardware, Firmware, Or Software
Power Delivery And Thermal
PSU rails that sag under load can light LEDs yet fail under GPU draw. Feel for heat. Clean vents. Spin fans by hand with power off. Try a known-good PSU if you have one. On laptops, test with the original charger and a direct wall outlet. Battery-only starts help isolate a bad brick.
Memory And Motherboard
Bad RAM can block POST or crash the boot loader. Run sticks one by one. If you reach Safe Mode with one module, you likely have a matched set issue or a weak slot. Inspect the board for bulged capacitors and scorched marks near VRMs. Clear CMOS with the jumper or a long battery pull and let the board redetect hardware.
Drives And Cables
Boot messages that mention “device not found” point at the cable or the drive. Swap SATA leads. Move the plug to a different port. On NVMe, reseat the blade and confirm the standoff screw is snug. Keep one bootable drive attached during tests to avoid stray entries.
Graphics Path
A black panel with a lit power LED often ties to a bad display path. Try the iGPU by removing the discrete card, then plug into the motherboard port. If the board lacks video, test the card in a second system.
Software And Updates
Driver stacks and failed updates can loop boot screens. In Safe Mode, remove the last GPU or storage driver you installed. Use System Restore to back up a step in time. If the system starts, set a restore point, patch in smaller bites, and retest after each change.
Deeper Repairs When Windows Still Won’t Boot
Rebuild The Boot Records
From a recovery command prompt, run bootrec commands in this order: bootrec /scanos, bootrec /rebuildbcd, bootrec /fixmbr, and bootrec /fixboot. Follow with a restart. If the BCD store was the snag, this step brings the logo back fast.
File System And Image Health
Use chkdsk /r on the system volume to scan and repair sectors. Then run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth from Safe Mode or from an offline mount. SFC swaps damaged protected files with clean copies. DISM repairs the component store that feeds SFC.
Last Resort Paths
When nothing sticks, a reset that keeps files can save your day, but always move backup copies to another device first. If resets fail, a clean install on a new drive avoids a second failure during install. Keep the old drive read-only until data is safe.
Boot Media And Recovery Paths
Keep a bootable USB around. One stick with Windows install media and one with a Linux live image covers most rescue cases. On Macs, recovery lives in firmware and can fetch what you need over Wi-Fi. Labels on each stick save guesswork later.
| Goal | You Need | Where To Start |
|---|---|---|
| Fix startup files | Windows USB or RE | Startup Repair, then Safe Mode |
| Recover files | Second drive or live USB | Copy data before resets |
| Fresh install | Install media | Clean install on a new drive |
Prevention: Build A Boot-Friendly Setup
Keep A Clean Boot List
Remove stale entries in firmware after you change drives. Disable network boot if you don’t use it. Label each internal drive by bay or slot and mirror that label in the case.
Backups You Can Restore Fast
Schedule an image backup to an external drive. Add a cloud folder for documents. Test a restore quarterly. A backup you haven’t tested isn’t a backup.
Patch With A Plan
Install driver and OS updates in smaller chunks. Reboot between chunks. Keep a restore point before a big GPU or storage driver change.
Hardware Hygiene
Dust filters, tidy cables, and stable power keep parts happy. A small UPS stops brownouts from corrupting writes. Replace aging SATA cables and thermal paste on a timer instead of waiting for a crash.
When To Call For Help
Stop and seek a bench test if you smell burnt resin, see arcing, or the drive clicks. Data first, fixes second. If the machine is under warranty, open a ticket before you open the case. Photo any damage before you move parts. Good notes speed an RMA.
For guided screens and exact keys, see Microsoft’s Startup Repair and Apple’s macOS startup keys. Bookmark both on a phone so you have them when the PC is down.