From: DX-MON on
Find the Automatic Updates files in System32 and the driver cache in System32, and delete them - then the virus scanner cannot use AU; either that, or de-install the anti-virus software provided by Microsoft - either of those will sort your problem out. The former is just a more bruit-force style (with no damage to your computer)

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frmsrcurl: http://compgroups.net/comp.os.ms-windows.programmer.win32/Automatic-updates-running-even-when-turned-off