Speed it up Windows XP & Windows 2000
Windows XP uses the Fast User Switching feature; you need not worry about shutting down the PC or closing all active tasks if someone needs urgent access to the computer . Enable Fast User Switching from Settings> Control Panel > User Accounts, and tick the Allow Fast User Switching feature under change the way user log on or off.
After that, in the Start menu, select Log Off, and the prompt, select Switch user instead of Log Off. Once you log back in under your profile, the system resumes with all processes and tasks, and applications pick up from where you left off.
Unlike XP, Windows 2000 doesn’t allow two user to log on simultaneously. For another user to take over, the current user has to log off first.