Solution 1. Perform a hard reboot
If your Windows cannot boot because of the "Preparing Automatic Repair" or "Diagnosing your PC" error, you can do a hard reboot.
- Remove the battery and AC adapter.
- Press and hold the power button for 20 seconds and see if it will boot up normally.
If this method doesn't work, try the following solutions.
Solution 2. Boot into safe mode
You can try the method below to enter into safe mode when you encounter any issues related to booting up your computer.
Step 1: Turn off your computer.
Step 2: Insert the Windows bootable installation disk to your PC and boot from it.
Step 3: When prompted to Press any key to boot from CD or DVD, press any key to continue.
Step 4: Select your language preferences in the Windows Setup interface, and click on Next button to continue.
Step 5: Tap or click on Repair your computer to continue.
Step 6: Select Troubleshoot.
Step 7: Click on Advanced options.
Step 8: Click on Startup Settings.
Step 9: Click on Restart. After restart, the computer will show another screen that has different startup options.
Step 10: On your keyboard, press the 4 or the F4 key to boot into minimal Safe Mode. (If you need to do some online research after booting into the safe mode, press 5 or F5 to boot into "Safe Mode with Networking.")