Network, Volume and Power Greyed out on Notification Area Icons ...

Problem:   You cannot see Volume icon on the Notification area in Vista. On clicking on taskbar properties, the options Volume, Power, Network etc are grayed out.

Solution:

Open the Start Menu.
In the white line (Start Search) area, type gpedit.msc and press Enter.
Click Continue for the UAC prompt.
In the left pane, click on User Configuration, Administrative Templates, Start Menu and Taskbar.

        In the right pane, right click on Remove the volume control icon and click Properties. To Enable the Volume Icon - Dot Disabled or Not Configured and click OK.

Note: But this method would not work on Vista Home Basic as Group Policy editor might not open. For this, follow steps as below:

Open regedit.

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

In the right pane of Explorer, right click on a empty area and click New -> DWORD (32-bit) Value

Type HideSCAVolume and press Enter

Close regedit

 Logoff and logon, or restart the computer to apply the changes.

Incase you already see the HideSCAVolume option, delete it.

Link: http://www.vistax64.com/tutorials/106787-notification-area-system-icons.html