on mine when windows xp starts up there is a blue screen with a plaer blue bar thru the middle that shows my profile and my individual icon, but sometimes if someone else has set up their own profile it comes up aswell, i think this is what henrys is on about.
if you use a modem (either olde worlde dial up or broadband) then I suspect the second "login" is the prompt to connect to the internet... if that is the case it's easy to make that automatic so it doesn't prompt you.