If your computer will not start, you might be able to start it in safe mode. In safe mode, Windows uses default settings (VGA monitor, Microsoft mouse driver, no network connections, and the minimum device drivers required to start Windows).
If your computer will not start after you install new software, you might be able to start it with minimal services in safe mode and then change your computer settings or remove the newly installed software that is causing the problem. You can reinstall the service pack or the entire operating system, if necessary.
If a symptom does not reappear when you start in safe mode, you can eliminate the default settings and minimum device drivers as possible causes of the computer's inability to start.
The startup options are:
Starts using only basic files and drivers (mouse, except serial mice; monitor; keyboard; mass storage; base video; default system services; and no network connections). If your computer does not start successfully using safe mode, you might need to use the Recovery Console feature to repair your system.
For more information, see To start the computer in safe mode
Safe Mode with Networking
Starts using only basic files and drivers, and network connections.
Safe Mode with Command Prompt
Starts using only basic files and drivers. After logging on, the command prompt is displayed instead of the Windows graphical interface.
For more information, see To start your computer at a command prompt
Enable Boot Logging
Starts while logging all the drivers and services that were loaded (or not loaded) by the system to a file. This file is called ntbtlog.txt and it is located in the %windir% directory. Safe Mode, Safe Mode with Networking, and Safe Mode with Command Prompt add to the boot log a list of all the drivers and services that are loaded. The boot log is useful in determining the exact cause of system startup problems.
Enable VGA Mode
Starts using the basic VGA driver. This mode is useful when you have installed a new driver for your video card that is causing Windows not to start properly. The basic video driver is always used when you start in Safe Mode (either Safe Mode, Safe Mode with Networking, or Safe Mode with Command Prompt).
Last Known Good Configuration
Starts using the registry information and drivers that Windows saved at the last shutdown. Any changes made since the last successful startup will be lost. Use Last Known Good Configuration only in cases of incorrect configuration. It does not solve problems caused by corrupted or missing drivers or files.
For more information, see To start the computer using the last known good configuration
Directory Service Restore Mode
This is for the server operating systems and is only used in restoring the SYSVOL directory and the Active Directory directory service on a domain controller.
Starts while sending debug information through a serial cable to another computer.
If you are using, or have used, Remote Installation Services to install Windows on your computer, you might see additional options related to restoring or recovering your system using Remote Install Services.