Hi Claudio,
Here is a link to Microsoft’s website that describes what system restore is and how to use it. You need to know that this is performing changes to your computer that may change the behaviour of installed software. It is possible that this may cause more problems than it will solve. Please keep this in mind when making a decision.
Also, the link below describes three procedures. The one you would be interested in is System Restore. This will simply restore your computer to an earlier restore point.
http://windows.microsoft.com/en-ca/windows-8/restore-refresh-reset-pc
-Luke