as for the top one, windows XP has a "switch users" feature. When enabled, you can "log off" the user (while not closing their programs) and login as a new user. So in actuality you have two logged in, one active. As for being a service, that could be useful, as for like a bot or such. Although, then u'll have people whom will exploit it to make mirc trojans run in the background as well. Also, there is a windrop bot (much faster also) that you can run as a bot (if that is your intent).