REG ADD "HKLM\SOFTWARE\Policies\Adobe\Acrobat Reader\8.0\FeatureLockdown" /v bUpdater /d 0 /t REG_DWORD /f
Note the 8.0 in that string... change it to 9.0 or whatever version you are running (best bet is to browse the registry for the specific string you need first). Don't forget to do a "change user /install" before and "change user /execute" after just to make sure.
It seems that in some cases, that may not even be enough to stop the Adobe Updater. The final nail in the coffin, so to speak, after performing the above is to go into the C:\documents and settings\all users\ directory and hunt down Adobe_updater.exe, then rename it to .old. That should put this problem in the ground for good.