Performing an Advanced or Safe Mode Boot

Windows 7 needs access to specific system files to start properly. If the required files are missing or corrupt, your computer won't start and you'll need to use the Startup Repair tool to try to resolve your computer's problem. Most of the time, repairing a damaged or missing file will fix such an issue; sometimes, you might need to continue troubleshooting to diagnose and resolve a deeper issue.

Usually a computer fails to start because something has changed and your computer doesn't like the change. For example, you might have installed an update for a device driver that caused a system-wide conflict or failed partway through. Or a program you installed might have modified the system's configuration in such a way that prevents normal startup. Whatever the cause of the problem, you can try to resolve it using safe mode.

In safe mode, Windows 7 loads only basic files, services, and drivers, including those for the mouse, monitor, keyboard, mass storage, and base video. The monitor driver sets the basic settings and modes for the computer's monitor, and the base video driver sets the basic options for the computer's graphics card.

Because safe mode loads a limited set of configuration information, it can help you troubleshoot problems. When you have finished using safe mode, be sure to restart the computer using a normal startup. You will then be able to use the computer as you normally would.

Several Safe Mode options are available. The option you use depends on the type of problem you're experiencing. The main options are:

• Repair Your Computer Runs the Startup Repair tool, which you can use to repair damaged or missing system files that are preventing startup, as well as to perform other recovery tasks.
• Safe Mode Starts the computer with only basic files, services, and drivers during the initialization sequence. The drivers loaded include those for the mouse, monitor, keyboard, mass storage, and base video. No networking services or drivers are started.
• Safe Mode With Networking Starts the computer with basic files, services, and drivers, as well as services and drivers needed to start networking.
• Safe Mode With Command Prompt Starts the computer with basic files, services, and drivers, and then starts a command prompt instead of the Windows 7 graphical interface. No networking services or drivers are started. Start the Explorer shell from the command-line interface by pressing Ctrl+Shift+Esc to open Task Manager, clicking File, clicking New Task (Run) to open the Create New Task dialog box, typing explorer.exe, and then clicking OK.
• Enable Boot Logging Turns on boot logging to create a record of all startup events in the log files.
• Enable Low Resolution Video Turns on low-resolution (640 x 480) display mode, which is useful if the system display is set to a mode that can't be used with the current monitor.
• Last Known Good Configuration Starts the computer in Safe Mode using registry information that Windows 7 saved at the last working shutdown. Only the HKEY_CURRENT_CONFIG (HKCC) hive is loaded. This registry hive stores information about the hardware configuration with which you previously and successfully started the computer.
• Disable Automatic Restart On System Failure Prevents Windows from restarting after a crash. If you don't set this option, Windows will restart automatically after a crash.
• Disable Driver Signature Enforcement Starts the computer in Safe Mode without enforcing digital signature policy settings for device drivers. This can temporarily resolve a startup problem related to a device driver with an invalid or missing digital signature. After your computer is started, you can resolve the problem permanently by getting a new driver or changing the driver signature enforcement settings.

You can start a computer in Safe Mode by completing the following steps:

1. If the computer is running but has started with errors, click Start. On the Start menu, click the Shut Down options button, and then click Restart.
2. During startup, press F8 to access the Advanced Boot Options menu.
   NOTE: If the computer has multiple operating systems or you've installed the Recovery Console, you'll see the Windows Boot Manager screen. Select Windows 7 as the operating system, and then press F8.
3. Use the arrow keys to select the mode you want to use, and then press Enter.
4. If a problem doesn't reappear when you start in Safe Mode, you can eliminate the default settings and basic device drivers as possible causes. Begin your troubleshooting by looking at newly added devices or updated drivers. Use Safe Mode to remove the devices, reverse the updates, or install different versions of driver software. Restart your computer to test your changes.
5. If you are still having a problem starting the system normally and suspect that problems with hardware, software, or settings are to blame, go back to Safe Mode and try using System Restore to undo previous changes.