The Stored User Names and Passwords applet lets you assign user names and passwords to use when needing to authenticate yourself to services in domains other than the one you are currently logged into.  The normal way of running this applet can be difficult to find quickly, so here is a way to launch it using a desktop shortcut using the rundll32.exe program:

Click on START - RUN and type the following (follwed by ENTER):

rundll32.exe keymgr.dll,KRShowKeyMgr