Black screen hp 520
Start the computer in safe mode and run System Restore:
Click the Start button Picture of the Start button, click the arrow next to Shut Down, and then click Restart.
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 must press F8 before the Windows logo appears. If the Windows logo appears, 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.
On the Advanced Boot Options screen, use the arrow keys to highlight Safe Mode, and then press Enter.
Log on to your computer with a user account that has administrator
rights. When your computer is in safe mode, you'll see the words Safe
Mode in the corners of your monitor.
Click the Start button Picture of the Start button, type "system restore" in the search box, click System Restore, and then click Next. Administrator permission required If you're
prompted for an administrator password or confirmation, type the
password or provide confirmation.
Choose a restore point when your PC worked as expected, click Next, and then click Finish.
Use system utility software like RegInOut after restarting windows normally. It will repair corrupt registry and windows files.