Pop-up notifications from system tray is called ballon tips.To disable balloon tips in windows XP
1.Click start button and click Run menu.
2.Type regedit and press OK.
4.Right-click in the right hand side pane and select New and choose DWORD Value from the popup menu.
5.Name it to EnableBalloonTips.
6.Double-click EnableBalloonTips.It displays Edit DWORD Value dialog box.
7.Enter 0 in the Value data edit box.
8.Close Registry Editor and restart your pc.
9.you should no longer have balloon tips.