HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main\
We added two String values in the right pane, "Window Title" and "WindowTitle" ("Window Title" is required with IE5 and/or Outlook 98). Now right-click each new value, click Modify and make the Window Title and WindowTitle (make sure the values are identical!) whatever you want it to be (our work machine says "My Browser").
And here is how we did it for Outlook Express:
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Outlook Express\
This time you only need the String "WindowTitle" and again you can
modify it to be whatever you wish.