If you can't start your PC, follow these instructions to get to the Windows Recovery Environment.

Get to Windows Startup Settings in the Windows Recovery Environment Sign in to your PC with a user account that has administrator rights. On the Startup Settings screen, choose the startup setting you want. Tap or click Startup Settings and then Restart. If you don't see the Startup Settings option, tap or click Advanced options. Once your PC restarts, on the Choose an option screen, tap or click Troubleshoot. Under Advanced startup, tap or click Restart now. Under PC settings, tap or click Update and recovery, and then tap or click Recovery. (If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.) Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. Get to Windows Startup Settings in PC settings With Windows Startup Settings you can start Windows in different advanced troubleshooting modes to help you find and fix problems on your PC.

Boot windows 7 in safe mode