In Security Center
you will see "Automatic Updates". If you see ON
next to it, you should change the setting as follows. Scroll down to the very bottom
of the window and click "Automatic Updates" under "Manage security settings for". A new, separate Automatic Updates
window will pop up. Select "Notify me but don't automatically download or install them", and click OK
. If you changed this setting, then downloading & installing Windows updates, including hopefully MSE definitions, has now become a controllable multi-step process for you. You will be notified via the taskbar when there are new updates available, but now you choose when to download them, and after they're downloaded you are notified and choose
when to install them (also handy since sometimes a reboot is prompted and you could be in the middle of something).