The reasons I would need to install XP, log in with a different user without closing another users programs nor being able to close them, AKA 'switch user'. AFAIK, for a windows machine XP is the only one capable of doing it.

I will need to take a computer from the office and leave it at home because I don't have one there, I will need one for those late night homework. So my computer will be accessed by other people, including my mother with the help of 'switch user'. My question, on a secure environment switch user is disabled, but I will need to use it. On the office lan, nobody knows how to use a computer very well much less to hack, so locally I'm not worried, but how about the internet?
With switch user enabled, is it easier for anybody to access my acount name?