Yes you can have it only do updates when you want. This removes the problem of it rebooting while you are working on something. However the offset is that you will have to tell Vista to download and install the updates regularly.
To change from Vista doing the updates automatically go to Control Panel which is found in your Start menu that appears when you click the Start button. Choose System and Maintenance and Windows Update if you are using the default view of Control Panel or if you are using the Classic View choose Windows Update. Choose Change Settings in the left column.
You could choose Never Check for Updates but I would not recommend it as you will have to remember every week to check for updates.
I suggest either using the Download updates but let me choose whether to install or the Check for updates but let me choose when to download and install. If you have a good Internet connection then Download is the better option. If you are on dial-up or other slow connection then Check is better. In either case when there are updates to download and/or install you will see a gold shield on the bottom right that will pop-up a message that updates are available when hovered over or when it appears.
Thank you Kristina for the question this week.