The Security Center application in Vista informs users about their security settings if not configured properly, by displaying a balloon in the system tray. At times, this could prove to be quite .irritating. If you would like to disable these prompts, follow the steps below:

Right-click the Security Center icon and select 'Open Security Center'.

Click the 'Change the way Security Center alerts me' link.

From the 'Do you want to be notified of security issues' window, click 'Don't notify me and don't display the icon (not recommended)'.