After removing a virus from a Windows XP computer, I got this message when I tried to turn on Automatic Updates: “Security Center could not change your Automatic Updates settings.” Viruses usually leave their little hooks behind after you uninstall them, disabling the tools that you need to fight them. So thanks to this page and this page, I found out how to turn Automatic Updates back on after the computer was clean of any more viruses. It’s all about registering some DLLs that got unregistered.
Click Start, select Run and type:
Press Enter after each one and wait for the success message
This worked to get my Automatic Updates turned back on, and my Windows Updates working again.