Windows 8 does not offer a desktop notification about new available Windows Updates. You can choose the option "Check for updates but let me choose whether to download them" within the Windows Update Settings, but you will not be informed about new updates via a popup on the desktop (as it was in windows 7). Only on the logon screen you can see a hint in the bottom right corner.
It informs about updates via a popup and it enables to open the windows update dialog directly by clicking the popup. The application only appears as an icon in the system tray so it will not interfere with your work.
Although the application is developed for Windows 8 it also works on Windows 7.
New functions/features to be added as development progresses (or put in your request to the deve.)
Simple non-install .exe: https://wun.codeplex.com/license