Doesn't seem to be a whole lot on the Internet about this.
I was tweaking the Local Security Policy of one of our test servers (Windows Server 2008 R2 Standard Service Pack 1), when I got this error. So then I used this hotfix, which caused DefaultAppPool and Classic .NET AppPool to suddenly disappear. So then I tried this fix to get them back.
The problem? Previously there were many entries in the Local Security Policy that just said, "DefaultAppPool" or "Classic .NET AppPool". Now it won't take either, but instead, I have to use "IIS APPPOOL\DefaultAppPool" or "IIS APPPOOL\Classic .NET AppPool".
Since the string that was added to the inf file in the third link included the "IIS APPPOOL\" prefix in both cases, I tried running secedit again, without that qualifier in the inf file. But then secedit couldn't find those users, as a result of the qualifier not being there.
So how do you get it back to where you don't have to use the "IIS APPPOOL\" prefix in the Local Security Policy?