Below is a compact, practical troubleshooting guide you can use for most operating system (OS) problems. Start with the general workflow, then use the targeted steps for common error types, plus useful commands/tools and prevention tips.

General troubleshooting workflow (quick checklist)

1. Reproduce the problem and note exactly what happened (error messages, codes, time).
2. Ask: did anything change recently? (updates, drivers, new hardware/software)
3. Isolate hardware vs software: try Safe Mode / Recovery / Live USB.
4. Check logs and error codes (Event Viewer, Console, journalctl, dmesg). Copy or screenshot messages.
5. Try non-destructive fixes first: reboot, disconnect peripherals, uninstall recent software/patches, roll back drivers.
6. Run filesystem, disk and memory checks. Backup important data before risky fixes.
7. If unresolved, escalate to system restore/rollback or OS repair tools. As last resort, reinstall OS (after backup).
8. Document what you tried and when. If contacting support, provide logs, steps, and system details.

Common problems, causes and targeted fixes

1. System won’t boot

• Symptoms: black screen, boot loop, “no bootable device”, GRUB errors, Windows recovery loop.
• Quick fixes:
  • Use Safe Mode (Windows: Shift+Restart → Troubleshoot → Advanced → Startup Settings; macOS: hold Shift at boot; Linux: choose Recovery/rescue or use a live USB).
  • Repair bootloader: Windows Recovery → Command Prompt → bootrec /fixmbr, /fixboot, /rebuildbcd. Linux: chroot from live USB and reinstall GRUB (update-grub / grub-install). macOS: Boot to Recovery (Cmd+R) → Reinstall or use Disk Utility.
  • If recent hardware change, remove it and try again.
• Diagnostics: check firmware/BIOS boot order, SMART disk health, fsck/chkdsk.

2. Blue Screen (BSOD) or Kernel Panic

• Symptoms: crash with stop code (Windows) or panic and restart (macOS/Linux).
• Steps:
  • Note stop code and any recently installed drivers. Boot to Safe Mode and uninstall suspect drivers.
  • Analyze minidump (Windows) with WinDbg or use online lookup of stop codes.
  • macOS: check panic logs in Console (/Library/Logs/DiagnosticReports or Console app).
  • Linux: inspect journalctl -k and /var/log/messages or dmesg for stack traces.
  • Run memory test (MemTest86) and SMART disk test.

3. Slow performance / high CPU, disk, memory usage

• Steps:
  • Check running processes: Windows Task Manager, macOS Activity Monitor, Linux top/htop.
  • Look for runaway processes, excessive disk I/O, or full swap.
  • Check startup programs and disable unnecessary ones (msconfig/Task Manager Startup, System Preferences → Users & Groups → Login Items).
  • Run antivirus/malware scan.
  • Free disk space (delete temp files, log files; use WinDirStat/du).
  • Update drivers and OS patches.
  • For persistent slowdown, consider SSD upgrade or adding RAM.

4. Update/upgrade failures

• Symptoms: updates fail repeatedly, error codes, update loops.
• Steps:
  • Windows: run Windows Update Troubleshooter, sfc /scannow, DISM /Online /Cleanup-Image /RestoreHealth, clear SoftwareDistribution folder, retry.
  • macOS: use Safe Mode or Recovery to reinstall. For App Store updates, sign out/in.
  • Linux: run package manager repair (apt --fix-broken install; dpkg --configure -a; yum/dnf repair steps).
  • Check disk space and network connectivity.

5. Application crashes or won’t start

• Steps:
  • Check application-specific logs and OS logs for errors.
  • Reinstall the app, remove corrupt preferences/config (move config files), run in compatibility mode (Windows).
  • Ensure dependencies (libraries, runtime) are installed and up to date.

6. File system corruption or “missing/corrupt files”

• Steps:
  • Backup important data immediately.
  • Windows: run chkdsk C: /f /r, sfc /scannow.
  • macOS: run Disk Utility → First Aid or boot to single-user and run fsck -fy.
  • Linux: run fsck on unmounted partition (from live environment).
  • Restore from backup or shadow copies if repair fails.

7. Network connectivity problems

• Steps:
  • Basic checks: physical connection, router/modem restart, try another device.
  • Commands: Windows ipconfig /all; release/renew with ipconfig /release and /renew; flush DNS ipconfig /flushdns. macOS: ifconfig, scutil --dns. Linux: ip addr, nmcli.
  • Test: ping, traceroute/tracert, nslookup/dig.
  • Disable VPN/proxy/firewall temporarily to test.
  • Update network drivers or firmware on router.

8. Driver or hardware device issues

• Steps:
  • Roll back or update driver (Device Manager on Windows, vendor drivers on macOS/Linux).
  • Uninstall device and reboot to let OS re-detect it.
  • Check vendor diagnostics and firmware updates.
  • Test device on another computer if possible.

9. Permission and access errors

• Symptoms: “Access denied”, can’t open or write files.
• Steps:
  • Windows: use takeown /f <file/folder> and icacls <file> /grant <user>:(F) to restore ownership/permissions.
  • macOS/Linux: check ownership with ls -l and use chown/chmod to fix; check ACLs and SELinux/AppArmor contexts (restorecon on SELinux).
  • Verify user account privileges and group membership.

10. Suspected malware or security breach

• Steps:
  • Disconnect from network if breach suspected.
  • Run full antivirus scans and offline/bootable scanners (Windows Defender Offline, other reputable scanners).
  • Check for unusual accounts, scheduled tasks, startup entries.
  • Change passwords from a different clean device.
  • Restore from known-good backup if persistence cannot be removed.

Useful commands & where to look for logs

• Windows:
  • Event Viewer: eventvwr.msc (Application, System, Security logs).
  • sfc /scannow (system file check).
  • DISM /Online /Cleanup-Image /RestoreHealth.
  • chkdsk C: /f /r.
  • bootrec /fixmbr /fixboot /rebuildbcd.
  • Memory Diagnostic: mdsched.exe.
• macOS:
  • Console app (logs), /Library/Logs/DiagnosticReports.
  • diskutil list; diskutil verifyVolume / repairVolume.
  • fsck -fy (single-user mode).
  • Reset NVRAM: Option-Command-P-R; reset SMC per model.
• Linux:
  • journalctl -b (current boot), journalctl -p err -b (errors).
  • dmesg | less, /var/log/syslog or /var/log/messages.
  • fsck /dev/sdXN (unmounted).
  • smartctl -a /dev/sdX (SMART disk status).
  • dpkg --configure -a, apt --fix-broken install (Debian/Ubuntu).

Hardware diagnostics

• Test RAM with MemTest86 (bootable).
• Check disks with SMART tools (smartctl, CrystalDiskInfo).
• Swap cables, try different SATA/USB ports, test storage on another machine.
• Overheating: check fans and temperatures (HWMonitor, sensors).

When to restore or reinstall

• If filesystem is badly damaged, malware persists after cleaning, or you can’t repair boot or core OS components, back up data and perform system restore (if available) or a clean OS reinstall. Try in-place repair first (Windows repair install, macOS reinstall from Recovery).

Prevention & good practices

• Keep backups (regular full+incremental; test restores).
• Keep OS and drivers updated, but delay critical updates briefly to watch for problem reports.
• Use reputable security software and enable firewall.
• Keep recovery media (bootable USB) and system restore enabled.
• Document system changes and create restore points before major updates.

When to get professional help

• Repeated hardware errors (SMART failures), failed RAID arrays, encrypted filesystem errors you can’t decrypt, or data you cannot recover—stop and consult a data-recovery professional. If under warranty, contact vendor support.

If you want step-by-step commands or a walk-through, tell me: which OS (Windows version, macOS version, or Linux distro & kernel) and the exact error message or behavior, and I’ll give a focused repair sequence.