By default, Windows 7 hides all icons present in the system notification area except Action Center, Network and Volume Mixer icons. This feature is very handy especially for those who would like to keep the notification area clutter free. The notification area can be expanded by clicking the tiny arrow icon present at the extreme left of the notification area (system tray).
Sometimes, Windows 7 may not hide notification area icons and display all hidden icons. To fix this issue, you need to follow the three simple steps:
1. Right-click on the empty space of Notification area (or simply right click on the Clock) and select Customize notification icons option to launch Notification Area Icons window.
2. Here, uncheck the box named Always show all icons and notifications on the taskbar.
3. Click Ok button to hide all icons present in the notification area. That’s it!
You might also like to read 7 free tools available to tweak and customize Windows 7 taskbar article.