Missing Taskbar icons Windows xp/vista/7
Missing Taskbar icons
If icons have disappeared from the Taskbar's notification area, there
are two things to try: first, press the Windows key and [R], type
"regedit" and press [Enter].
Browse to HKEY_CURRENT_USER\ Software\Classes\Local
Settings\Software\Microsoft\Windows\ CurrentVersion\TrayNotify, and
delete both IconStreams and PastIconsStream values.
Reboot, or
log off and back on again. If the problem persists in XP, and you can
live without it, open the Add or Remove Programs Control Panel, click
Add/Remove Windows Components, expand Networking Services, and untick
"UPnP User Interface". Then click OK > Next.