Hi riccardo12,
Could you please run FRST64 again using the following script, the registry key in question appears to be causing problems and therefore we'll delete it and see if it then allows you to install the update. The script will create a system restore point beforehand and then should reboot your computer. After the system has successfully rebooted, then please attempt to install the Windows update from earlier again.
FRST Fix
NOTICE: This script was written specifically for this user, for use on that particular machine. Running this on another machine may cause damage to your operating system
1. Download attached file and save it to the Desktop.
Note. It's important that both files, FRST64 and fixlist.txt are in the same location or the fix will not work (in this case...the desktop).
2. Run FRST64 by Right-Clicking on the file and choosing Run as administrator.
3. Press the Fix button just once and wait. If for some reason the tool needs a restart, please make sure you let the system restart normally. After that let the tool complete its run.
4. When finished FRST64 will generate a log on the Desktop (Fixlog.txt). Please post the contents of it in your reply.