What is your operating system?
Did you get this screen?
If your laptop is a recent purchase, Windows must be activated otherwise after a time, the system gets blocked.
Re-entering the product key that came with your lappy or original copy of Windows might solve the problem.
My problem is that, after the message that I should activate my windows I can't access my settings to re-enter my procudt key again
no, I got a screen saying I should activate my windows 8, then when I click on activate the screen turns blue and then back to start menu. I cant even put a wallpaper on my desktop background
Sony E-series Model - SVE151L11W
Will it boot in safe mode with networking?
You can hold down the SHIFT key while clicking on Restart to be taken to the troubleshooting option screen where you can enable Safe Mode with Networking.
You can see these other options to get into safe mode with networking.
If you can get into safe mode with networking I should be able to send you a tool which should explain the reason for the blue screen of death.