I met with Microsoft Assure program a few days ago. It is a assistance service on remote desktop. The microsoft technicians connect to your pc and give asisstance to the problems.
On our issue, my client delete all admin permissions and even administrator group's privileges on drive C:/. solutions I found on internet doesn't work but with Assure assistance, we're able to take back all permissions back. The tech guy didn't give up and remotetly connects 5 time between 3 days then he found the problems one by one and get there. It's worth to money not only for year but for that specific fix I think.