this is odd - it sounds like you are (or at least have been) part of a domain.
unfortunately - while it's easy to config in XP pro = in home ... it's a pig
XP home isn't really meant to do this - so it's a bodge
there is a free utility to set up access ... so
http://www.x-setup.net/downloads/home.asp
and it should also make it easy to remove
open - goto
network | windows | Setup - clear the domain info - reboot ... and that's it
you can also configure auto logon for windows as well ... so it will (should) solve all your problems
but be warned - this is a system tweaker ... it's good - there are tons of "improvements" available
... but it can be dangerous
you can easily "configure" your system into the dustbin ... be careful - and don't get too off road
http://www.staffkit.com/resources/join_domain_ windows_xp_home.htm