Why are all the topics I can be helpful in get locked, damn.
\HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\
\HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\
\HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\Results
\HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\Results\Detect
\HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\Results\Download
\HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\Results\Install
These registry keys have values that should give you adequate information to detect if an Windows Update is in progress, especially the latter three I listed.