can administrator log on as other user?

Many times I, as the administrator of a domain, would like
to log into a Windows 2000/XP machine as a particular
ordinary user to change settings, troubleshoot
permissions, etc... Is there any way for an account with
administrator access to assume the identity of another
user (as with the su command of *nix)?

Can this be done in the middle of a session where I have
logged in as Administrator?

I know about the runas command, but it's a hassle to do
this for many programs in a row, plus it doesn't allow me
to easily see what the user sees as far as desktop, screen
resolution, etc...

Thanks in advance for any help you may be able to provide.

Peter