The Automatic Update client maintains its operational state in the following registry key:
Key: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\
Value: AUState

AUState values
0 Initial 24 hour timeout (the AU wizard does not run until 24 hours after it first detects an Internet connection)
1 Waiting for user to run AU wizard
2 Detect pending
3 Download pending (waiting for user to accept pre-download prompt)
4 Download in progress
5 Install pending
6 Install complete
7 Disabled (Adoptions will also be set to a value of 0x1)
8 Reboot pending (updates that require a reboot were installed but the reboot was declined – AU will not do anything until the reboot occurs and this value is cleared)