HiFernandoRLD**,**I would suggest you to place the computer in Clean Boot follow step1 to place the computer in clean boot and then try to install the article KB947821 and see if you are able to install , once you install then download and install windows7 service pack1 from the following link.
Windows 7 and Windows Server 2008 R2 Service Pack 1 (KB976932)
once you install windows 7 service pack1, don’t forget to put the computer back to the normal mode follow step7 from clean boot article.