runas keeps coming back with access denied in Windows

Q: I have a problem running a process using the runas command in Windows 2000/XP even through I have the userid and password correct, it keeps coming back with access denied

A: The problem is likely to be that the runas service is not running – see http://support.microsoft.com/default.aspx?scid=kb;en-us;294676 for details on starting it.