HI sergeli:
Welcome to the HP forum!
Thank you for your query. I will endeavor to do my best for you!
I perceive that after upgrading to Windows 8.1, you are now getting a black screen at startup.
Here is a link to Troubleshooting Black Screen Displays with No Error Messages During Startup or Boot. If you are unable to resolve the boot issue, I would do a recovery back to Window 8 .Performing an HP System Recovery (Windows 8). Here is a document I recommend reading, before you try to update again. Updating Windows 8 to 8.1. I hope this has helped. Please do not hesitate to re-post if you have any other concerns.