If you are running on Windows 2008 or Vista or above, then the Administrator account has two sets of authorities. This is built in to Windows and you cannot change this behaviour.
One set of authorities gives you standard 'User' rights, and one gives you the 'Administrator' rights. If you run a program without explicitly asking for Administrator rights, then you will run it as a normal user. This is why your SP4 install is failing.
It is worth investigating with Google how Administrator accounts get their rights - things changed in 2006.
Original author: https://github.com/SQL-FineBuild/Common/wiki/ 1-click install and best practice configuration of SQL Server 2019, 2017 2016, 2014, 2012, 2008 R2, 2008 and 2005.
When I give food to the poor they call me a saint. When I ask why they are poor they call me a communist - Archbishop Hélder Câmara