Windows XP SP3 blocks uninstall of software

As previously reported, Windows XP with Service Pack 3 has a nasty tendency to cause people to be unable to uninstall software such as Internet Explorer 7 and Internet Explorer 8.
 
What I didn’t know, was that it doesn’t confine itself to blocking uninstall of these programs, but that it also blocks the uninstall of, for example, Lotus Notes.
 
I even got an error message; this one, to be exact: “The Windows Installer Service Could Not Be Accessed”
 
It would seem that Service Pack 3 actually blocks software from accessing the Windows Installer Service. The solution, then, is to uninstall Service Pack 3. After I did that, I could uninstall Lotus Notes.