This guide details how you can troubleshoot and fix a computer that won’t start (or won’t boot).

This guide goes through various solutions and fixes that you can apply for most Windows versions: XP, Vista, 7, 8, 8.1 and 10.

Fix with Easy Recovery Essentials

Using Easy Recovery Essentials (EasyRE) and its built-in Automated Repair process, you can find and fix various boot errors that prevent your computer from starting.

Everything is done in one single-click:

Download Easy Recovery Essentials by clicking this link.

General fixes if Windows won’t start

Fix #1: Boot into Last Known Good Configuration

If Windows doesn’t start, booting in the Last Known Good Configuration mode usually fixes this.

To boot into this mode, follow these steps:

1. Restart your computer
2. Press the F8 key before the Windows logo appears
3. At the Advanced Boot Options menu, select Last Known Good Configuration
4. Press Enter

Fix #2: Boot into Safe Mode

Here are the steps you need to follow to boot into the Safe Mode of your computer:

1. Restart your computer
2. Press the F8 key repeatedly as soon as your computer boots, but before the Windows logo appears
3. Select Safe Mode at the Advanced Boot Options menu
4. Press Enter

You can now try to uninstall recently added hardware drivers or software applications.

Fix #3: Remove recently added hardware

If you recently added a new piece of hardware, follow these tips:

• Remove the new added hardware and restart your computer to check if it now starts and boots correctly.
• Remove any external hardware from your computer, except your mouse and keyboard. Restart your computer to test if it boots correctly.

Fix #4: Run chkdsk and sfc

The chkdsk and sfc utilities, part of Windows, can detect issues with your HDD. To run chkdsk and sfc, follow these steps:

1. Open Command Prompt via the Windows original installation disc
2. Type:

   chkdsk C: /r

   Replace C: is the letter of the drive where Windows is installed.

3. Press Enter
4. Type:

   sfc /scannow /offbootdir=c:\ /offwindir=c:\windows

   Replace c: with the letter of the drive where your Windows XP is installed.

5. Press Enter
6. Type exit and press Enter. Restart your computer.

If you don’t have the original Windows disc, use Command-line from Easy Recovery Essentials (our recovery and repair disc) to run these commands:

To download Easy Recovery Essentials, click here.

Fix #5: Run msconfig

If Windows won’t start because of a recently added software that runs at startup, you can use the msconfig utility to disable startup services or software applications:

1. Boot your computer into the Safe Mode mode
2. Click Start
3. Click Run and type msconfig or search for msconfig directly
4. Go to the Startup or Services tab
5. Disable all services listed in this tab
6. Click OK
7. Click Restart to restart your computer

Fix #6: Check for viruses

If you don’t have an antivirus software that you can use, get Easy Recovery Essentials and use built-in antivirus scanner which can run outside Windows, if you can’t boot into your computer:

The Professional Edition of Easy Recovery Essentials for Windows features a powerful antivirus and rootkit scanner that can normally resolve this and similar errors caused by viruses, rootkits, trojans, or spyware. EasyRE is currently available for Windows XP, Vista, 7 and 8 and can be downloaded and created on any PC.

You can download Easy Recovery Essentials from here.

Fixes if Windows Vista or 7 won’t start

Before following these fixes, go to General fixes if Windows won’t start.

Fix #1: Run Startup Repair

To run Startup Repair, follow these steps:

1. Insert the original Windows Vista or 7 installation disc
2. Restart the computer and press any key to boot from the disc
3. Click Repair your computer
4. Choose your operating system and click Next to continue
5. At System Recovery Options, select Startup Repair
6. After Startup Repair is done, restart your computer

Fix #2: Restore the MBR

Restoring the MBR of your computer might fix the computer to boot again. To do so, you need to run the bootrec utility:

1. Insert the Windows Vista or Windows 7 install disc and restart the computer
2. Boot from the disc
3. Click Repair your computer
4. Select Command Prompt at the System Recovery Options screen
5. Type:

   bootrec /FixMbr

6. Press Enter
7. Type:

   bootrec /FixBoot

8. Press Enter
9. Type:

   bootrec /RebuildBcd

10. Press Enter
11. Type:

    exit

12. Press Enter
13. Restart your computer

Fix #3: Disable Automatic Restart

Disabling the Automatic Restart option on a Windows Vista or 7 system might work and make the computer boot again.

To do so, perform these steps:

1. Restart the computer
2. Press the F8 key as soon as the computer starts to boot, but before the Windows logo appears on your screen
3. Select Disable automatic restart on system failure
4. Press Enter

Fix #4: Use System Restore

With System Restore, you can revert your computer to a working state earlier in time.

Since you can’t start Windows, you can run System Restore from Safe Mode:

1. Start the PC and press the F8 key repeatedly until the Advanced Boot Options menu appears
2. Select Safe Mode with Command Prompt
3. Press Enter
4. Type:

   rstrui.exe

5. Press Enter
6. Follow the wizard instructions to choose a restore point

If you can’t access the Advanced Boot Options menu, Easy Recovery Essentials also lets you access restore points from an external DVD or USB drive.

Fixes if Windows 8 won’t start

Before following these fixes, go to General fixes if Windows won’t start.

Fix #1: Restore the MBR

Similarly to the Windows Vista or Windows 7 steps to restore the MBR, use the Windows 8 DVD or USB to perform the same bootrec commands:

1. Insert the installation media, the DVD or the USB, and boot from it
2. Click Repair your computer
3. Click Troubleshoot
4. Click Advanced options
5. Click Command Prompt
6. Type:

   bootrec /FixMbr

7. Press Enter
8. Type:

   bootrec /FixBoot

9. Press Enter
10. Type:

    bootrec /ScanOs

11. Press Enter
12. Type:

    bootrec /RebuildBcd

13. Press Enter

Fix #2: Refresh or Reset

Windows 8 or Windows 8.1 can be refreshed or reseted. These 2 operations – Refresh or Reset – can be used to fix a non-working Windows.

To perform a Refresh, follow these steps:

1. Restart the computer
2. Insert the Windows 8 or 8.1 installation DVD and boot from it
3. Click Repair your computer
4. Click Troubleshoot
5. Click Refresh your PC

To perform a Reset, follow these steps:

1. Insert the installation media and boot from it
2. Click Repair your computer
3. Click Troubleshoot
4. Click Reset your PC

Fixes if Windows 10 won’t start

Before following these fixes, go to General fixes if Windows won’t start.

Fix #1: Restore the MBR

Similarly to the Windows Vista 8 steps to restore the MBR, use the Windows 10 DVD or USB to perform the same bootrec commands:

1. Insert the installation media, the DVD or the USB, and boot from it
2. Click Repair your computer 
3. Click Troubleshoot
4. Click Advanced options
5. Click Command Prompt
6. Type:

   bootrec /FixMbr

7. Press Enter
8. Type:

   bootrec /FixBoot

9. Press Enter
10. Type:

    bootrec /ScanOs

11. Press Enter
12. Type:

    bootrec /RebuildBcd

13. Press Enter

Fix #2: Refresh or Reset

Windows 8 or Windows 8.1 can be refreshed or reseted. These 2 operations – Refresh or Reset – can be used to fix a non-working Windows.

To perform a Refresh, follow these steps:

1. Restart the computer
2. Insert the Windows 8 or 8.1 installation DVD and boot from it
3. Click Repair your computer
4. Click Troubleshoot
5. Click Refresh your PC

To perform a Reset, follow these steps:

1. Insert the installation media and boot from it
2. Click Repair your computer
3. Click Troubleshoot
4. Click Reset your PC

More Information

Linked Entries

Applicable Systems

This Windows-related knowledgebase article applies to the following operating systems:

• Windows XP (all editions)
• Windows Vista (all editions)
• Windows 7 (all editions)
• Windows 8 (all editions)
• Windows 8.1 (all editions)
• Windows 10 (all editions)

Propose an edit

This article describes what to do if Firefox doesn’t open when you click the Firefox icon.

• If you get a message you can dismiss (e.g. “TypeError: Components.classes[‘@ … ;1’] is undefined”, “onload error TypeError: …”, “Exc in ev handl: …”) and can open Firefox, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.
• If Firefox starts but won’t load any websites, see Websites don’t load – troubleshoot and fix error messages.

Note: The

Troubleshoot Mode

Safe Mode

by

holding down the

shift

key while starting Firefox.

holding down the

option

key while starting Firefox.

quitting Firefox and then going to your Terminal and running: firefox -safe-mode
You may need to specify the Firefox installation path (e.g.

/usr/lib/firefox

)

The Refresh Firefox feature can fix many issues by restoring Firefox to its default state while saving your essential information. Consider using it before going through a lengthy troubleshooting process. The Firefox

Troubleshoot Mode

Safe Mode

window includes a Refresh Firefox option. You can start Firefox inby

Specific error messages

Mozilla Crash Reporter

If you get the “Mozilla Crash Reporter” window when you start Firefox, see Troubleshoot Firefox crashes (closing or quitting unexpectedly) for solutions.

Firefox is already running but is not responding

See “Firefox is already running but is not responding” error – How to fix for solutions.

Your Firefox profile cannot be loaded. It may be missing or inaccessible

See How to run Firefox when your profile is missing or inaccessible for solutions.

Failed to read the configuration file

This error is caused by a problem with Firefox program files. The solution is to remove the Firefox program and then reinstall Firefox. (This will not remove your passwords, bookmarks or other user data and settings which are stored in a separate profiles folder.)

1. Uninstall Firefox.
2. Delete the Firefox installation directory, normally found in one of these locations by default:
   • C:\Program Files\Mozilla Firefox
   • C:\Program Files (x86)\Mozilla Firefox
3. Use another browser to download the Firefox installer from the Firefox download page and install it. See How to install Firefox on Windows for details.

XULRunner – Error

If you see the message, “XULRunner – Error: Platform version <x.x.x.x> is not compatible with minVersion <x.x.x.x>”” (“<x.x.x.x>” depends on version number), after a software update, use another browser to download the Firefox installer from the Firefox download page, save it to the desktop or other location, delete the Firefox installation directory and then reinstall Firefoxreinstall Firefoxreinstall Firefox. If Firefox still does not start, see the Firefox will not start due to security software section below.

There was an error launching the application

This error indicates that either Firefox is not installed or your shortcut to it is incorrect. Make sure that Firefox is installed at the location specified by the shortcut. If it isn’t, install Firefox if necessary, then modify the shortcut to point to the correct location.

Error opening file for writing…

If you receive the above error when launching Firefox on a Windows system, you may be required by Firefox to log in as an administrator. You can either reboot the computer or, if you have an administrator account, you can execute the program as an administrator.

1. Find the

   firefox.exe

   program file in the Firefox application folder on your system.

2. Right-click the icon.
3. Select

   Run As Administrator…

   . Select The following user:. From the User name drop-down, select Administrator or another user that has administrator privileges. Enter the password required to log in to this account. Click

   OK

   .

4. The Firefox application is started using the administrator Windows account. The user that was used to log in to Windows at startup is still the active one.

Other error messages

If you get another error message (e.g. “XML Parsing Error: undefined entity Location”, “Secure Connection Failed … uses an invalid security certificate”), see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

No error message

If you click the Firefox icon but no Firefox window opens and no error message is shown, a simple first step is to restart your computer and then try again. If Firefox still does not start, see the following sections.

Firefox will not start due to security software

• Outdated versions of Comodo Firewall or Comodo Antivirus security software (or a leftover file after Comodo was uninstalled) can cause Firefox not to start with no error message. Update Comodo to the latest version, if you have it installed. If Comodo software is not installed, check if there’s a file called

  IseGuard64.dll

  or

  IseGuard32.dll

  in your

  C:\Windows\system32\

  folder or your system drive and, if so, manually delete the file.

• If you use certain versions of ZoneAlarm or other Internet security software that includes a “Virtual Browsing” feature, it can prevent Firefox from starting. Check virtualization settings and clear the virtual cache, if your Internet security software includes this feature, or visit the software provider’s support site for more help.
• Firefox may fail to start for some Windows users after updating, if AVG or AVAST antivirus is installed. For details, see this Techdows article.

Firefox will not start after installing add-ons

If Firefox previously worked but stopped after you installed extensions or themes, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Firefox previously worked

If Firefox previously worked but suddenly doesn’t start, it may be due to some corrupt data in your settings. Uninstalling and reinstalling Firefox would not fix this problem because your settings are not removed on uninstall.

To test to see if this is the problem, use the Profile Manager to create a new profile. If the problem goes away, you can then move your bookmarks and other important settings into the new profile.

Firefox will not start because of missing libraries

If you installed Firefox outside of your package manager, make sure that your system has the libraries listed in the system requirements.

Based on information from Browser will not start up (mozillaZine KB)