If your System Tray Notification Area Icons are missing or have disappeared in Windows Vista
If you find that your System Tray Notification Area Icons, like Clock, Volume, Network or Power are missing or have disappeared in Windows Vista, here is what you may try:
Right Click Taskbar > Properties > Notification Area Tab > System Icons > Check Desired Icon/s > Apply > OK.
If this does not solve your problem, or if you find that the areas are grayed out, try this:
Create a System Restore Point first, so that you have something to fall back on, should something go wrong. Before touching the registry, I always recommend creation of one!
Type Regedit in Vista's Start Menu Search Bar and hit enter.
From the Edit Tab, select Find, type and search for 'iconstreams' and then later for 'pasticonstreams' AND DELETE ALL such found instances of each of them.
On my Vista I found their first instance in Key:
HKEY_USERS \ S-1-5-21-2193082411-1103859620-1337499753-1000 \ Software \ Classes \ Local Settings \ Software \ Microsoft \ Windows \ CurrentVersion \ TrayNotify
Reboot.
Now enable the system icons using the above regular method. Do note that in case your computer has multiple user accounts you may have to enable icons for each account.