Users folder set to read-only

Hello,

I would like to thank you in advance for the time you dedicate to those of us who find ourselves struggling with our computers and I hope you can help me.

I should specify that I have a PC equipped with Windows 7.

While trying to save a file in My Pictures, I received an error message that prevented me from saving the file in the intended location. After going into the folder, I right-clicked - properties, and noticed that the box “read-only (applies only to files in this folder)” was checked (with a blue square and not a checkmark). I then tried to save the file on the desktop, but received the same error message. After checking, this problem extends to the entire C:\Users folder. When I uncheck it and click OK, the issue persists.

Additionally, when I open an Excel or Word file from My Documents, it is clearly indicated at the top of the window the name of the file followed by “read-only.”

I have researched on Google, followed advice that asked me to click on properties, then on the security tab, to uncheck the “full control” box, etc. but it did not work. For example, I cannot uncheck the “full control” box which is grayed out.

I also discovered that among the names of groups or users, there was “unknown account (S-1-5-21-3936550125-2326157420-4208807668-1001).” When I click on modify, a new window opens, I select this account and click on delete but an error message appears, saying that this object inherits its permissions from its parent. So, I do not know how to delete it and whether it is a sign of something serious.

I ran an Avast scan which took an extremely long time and I stopped it midway because it was stuck at 5% (it seemed that Avast was continuing its scan, but veeeeeery slowly). I ran a scan via Total AV, but it detected nothing.

Best regards.

Configuration: Windows / Chrome 83.0.4103.116