Can you change "logged-in" user without explicitly logging off?

From: Matt (anonymous_at_discussions.microsoft.com)
Date: 04/21/04 

Date: Tue, 20 Apr 2004 16:11:58 -0700

Just wondering if it is possible to change the user that
is currently "logged-in" without explicity logging off?

For example:

User A is logged in with user A's settings

<magic>

User B is logged in with user B's settings

Is there any <magic> to do this without User A logging off?

Thanks,

Matt.