Safe boot sequence - A+

https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode

The Advanced Boot Options screen lets you start Windows in advanced troubleshooting modes. You can access the menu by turning on your computer and pressing the F8 key before Windows starts.

Some options, such as safe mode, start Windows in a limited state, where only the bare essentials are started. If a problem doesn't reappear when you start in safe mode, you can eliminate the default settings and basic device drivers and services as possible causes. Other options start Windows with advanced features intended for use by system administrators and IT professionals. For more information, go to the Microsoft website for IT professionals.

Repair Your Computer

Shows a list of system recovery tools you can use to repair startup problems, run diagnostics, or restore your system. This option is available only if the tools are installed on your computer's hard disk. If you have a Windows installation disc, the system recovery tools are located on that disc.

Safe Mode 

Starts Windows with a minimal set of drivers and services.

To start in safe mode:

1. Remove all floppy disks, CDs, and DVDs from your computer, and then restart your computer. Click the Start button , click the arrow next to the Shut Down button (or the arrow next to the Lock button), and then click Restart.
2. Do one of the following:
• If your computer has a single operating system installed, press and hold the F8 key as your computer restarts. You need to press F8 before the Windows logo appears. If the Windows logo appears, you'll need to try again by waiting until the Windows logon prompt appears, and then shutting down and restarting your computer.
• If your computer has more than one operating system, use the arrow keys to highlight the operating system you want to start in safe mode, and then press F8.
3. On the Advanced Boot Options screen, use the arrow keys to highlight the safe mode option you want, and then press Enter.
4. Log on to your computer with a user account that has administrator rights.

• Safe Mode with Networking. Starts Windows in safe mode and includes the network drivers and services needed to access the Internet or other computers on your network.
• Safe Mode with Command Prompt. Starts Windows in safe mode with a command prompt window instead of the usual Windows interface. This option is intended for IT professionals and administrators.
• Enable Boot Logging. Creates a file, ntbtlog.txt, that lists all the drivers that are installed during startup and that might be useful for advanced troubleshooting.
• Enable low-resolution video (640×480). Starts Windows using your current video driver and using low resolution and refresh rate settings. You can use this mode to reset your display settings. For more information, see Change your screen resolution.
• Last Known Good Configuration (advanced). Starts Windows with the last registry and driver configuration that worked successfully. 
• Directory Services Restore Mode. Starts Windows domain controller running Active Directory so that the directory service can be restored. This option is intended for IT professionals and administrators.
• Debugging Mode. Starts Windows in an advanced troubleshooting mode intended for IT professionals and system administrators.
• Disable automatic restart on system failure. Prevents Windows from automatically restarting if an error causes Windows to fail. Choose this option only if Windows is stuck in a loop where Windows fails, attempts to restart, and fails again repeatedly.
• Disable Driver Signature Enforcement. Allows drivers containing improper signatures to be installed.
• Start Windows Normally. Starts Windows in its normal mode.