The system tray, also called the notification area, is the small area on the far right side of the taskbar, in which utilities and programs that run in the background, such as antivirus software, show their icons. I don’t find it a particularly intelligent use of screen real estate, so I prefer not to see the icons there.
To hide them, run the Registry Editor and go to the following key:
HKEY_CURRENT_USER/Software/Microsoft/Windows/CurrentVersion/Policies/Explorer. Among other things, this key controls the display of objects throughout XP. Create a new DWORD called NoTrayItemsDisplay. Assign it a value of 1. (A value of 0 will keep the icons displayed.) Exit the Registry and reboot.
While you’re at the HKEY_CURRENT_USER/Software/Microsoft/Windows/ CurrentVersion/Policies/Explorer key, you can also delete the My Recent Documents icon on the Start menu. Create a new DWORD called NoRecentDocsMenu. Assign it a value of 1. (A value of 0 will keep the icon displayed.) Exit the Registry and reboot.
"Windows XP Tips: Hide All Icons Notification Area"
Reference : techpraveen.com