Try restarting the computer using "last known good configuration":
1. Start Windows, or if it is running, shut Windows down, and then turn off the computer.
2. Restart the computer. The computer begins processing a set of instructions known as the Basic Input/Output System (BIOS). What is displayed depends on the BIOS manufacturer. Some computers display a progress bar that refers to the word BIOS, while others may not display any indication that this process is happening.
3. As soon as the BIOS has finished loading, begin tapping the F8 key on your keyboard. Continue to do so until the Windows Advanced Options menu appears. If you begin tapping the F8 key too soon, some computers display a "keyboard error" message. To resolve this, restart the computer and try again.
4. Using the arrow keys on the keyboard, scroll to and select the Last Known Good Configuration menu item, and then press Enter.