While logged in (XP prof.) as one user running Notepad, Firefox or any other
application, I can’t run the same application using “run as”. I have tried
both the “run as” meny-option and the “runas” cmd command.

What happens is that the application starts with the same credentials as the
current user! It doesn’t matter what user I have used for the run as
authentication (admin or limited user).

If the current user is not running the application, the run as function runs
as expected, with the credentials of the user used for the run as
authentication.

Does anyone know if this IS an XP limitation, or if there is a way to change
this behaviour?