By default, Windows Vista automatically hides icon in the notification area that are deemed unimportant or not used in a while. If you are like me and like to stay aware of what is running in the southeast corner of your screen, follow these easy steps:
1. Right-click the taskbar, choosing "Properties".
2. When the "Taskbar and Start Menu Properties" multi-tabbed dialog box appears, click the "Notification Area" tab.
3. Uncheck "Hide inactive icons".
4. Click "OK" to close the dialog box.
Conversely, if your inactive icons are not hidden and you would Vista to do so, ensure that step 3 above is checked.