Hi Nicolao,
Please follow the below steps and let me know the status.
Step 1: Run the system file checker tool.
Check the article http://support.microsoft.com/kb/929833 “How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7”
Step 2: Run the System Update Readiness Tool again. If the errors have been cleared, try installing Service Pack 1 again.
http://support.microsoft.com/kb/947821
If not, move to step 3.
Step 3: Perform a Startup Repair, upon startup, try installing the Service Pack.
“Learn how to install Windows 7 Service Pack 1 (SP1)”: http://windows.microsoft.com/en-US/windows7/learn-how-to-install-windows-7-service-pack-1-sp1
,
and then type Command Prompt.
If you're
prompted for an administrator password or confirmation, type the password or provide confirmation.