Is there a way I can access the system tray items using the keyboard in Windows XP?
You can move the keyboard focus directly to the systray area (system notification icons) with Win+B.
After selecting an icon with the arrow keys, you can simulate a left-click with Space (or maybe Enter), and a right-click with AppMenu (context menu key) or Shift+F10.
N.B. Using this method, some Windows XP users might not be able to see the 'focus' in the System Tray. If you press Win+B and it appears that nothing has happened, don't be put off. Try pressing → once or twice and then Shift+F10, and you might find it works regardless. (By contrast, using this method may be more likely to let you see the 'focus'. The 'active' icon should be highlighted in a rectangle formed of thin dotted lines.)
Tap the "Windows" key to open the start menu, but then press escape. You have just made the menu bar come into context for the keyboard. Now you can tab through the major areas of the menu bar, such as quickstart, toolbars and SysTray. Once tabbed into SysTray, you can use the arrow keys to select a specific icon and the menu key to simulate a right-click.
i create an autohotkey script that allows to activate the desired icon using right control and a number. The number depends on the order of appeareance of the icon. You could modify the source to adjust yours needs. Here is the full code with explanation hotkey for the systray