missing registry key

After failed sp2 install, looked in setupapi log
HKLM\Software\Microsoft\InternetExplorer\MAIN\Feat ureControl\FEATURE_DISABLE_MK_PROTOCOL
said Access denied, so I went into regedit and saw that Feature Control
is missing under the "...MAIN" folder. There are two files there, and
Feature Control is not one of them.
There are two other "Access denied" error messages in setupapi:
[Product.Add.Reg] in "c:\d11d8fa80d462c219324\i386\update\update.in f"
failed
and [ProductInstall.GlobalRegistryChanges.Install] at the same
location, also failed
What do I do about the missing registry item? And what do the other
two errors mean?