I don't know why Administrator privileges would be required. Someone else reported that recently on Reddit. Here is what I suggested to them:

You could try using cmd.exe. If you do a search in the Windows system search box for cmd.exe, it should come up with a Run as Administrator option (screenshot attached):

Then in the little command window you can type or paste the "change directory" command:

cd %USERPROFILE%\Desktop

Here you can do some damage, so carefully type or paste the "remove directory" command:

rmdir /S "Old Firefox Data"

It will ask you to confirm. After you type y <enter> it should remove the folder and all its contents.

You can type or paste

exit

to close out cmd.exe.

Success?

I tried that earlier today and it didn't work. I'll give it another shot, but doubtful.

I get an error message on entering: cd %USERPROFILE%\Desktop It says the path isn't found.

I get an error message on entering: cd %USERPROFILE%\Desktop It says the path isn't found.

That's strange! Can you cd to the root of the C drive and then navigate step by step?

cd C:\

cd users

cd <your user name>

cd desktop

That "Old Firefox Data" folder is hung up with One Drive. Even after I went to a help desk where I bought the PC it's still updating to friggin One Drive. This sucks.