Vista - public folder sharing/on (password required)

i have a vista desktop(hard wired to the router) a vista laptop (wireless) a
2nd XP desktop (hardwired) and 2nd XP laptop (wireless), before Vista, i
could get files and make changes to all computers from any where, now it says
that i have to enter a user and password when i chose a computer i want to
access. i have resetup the network 2 times, and each time i have NOT setup
with passwords, is there default passwords? i feel like i have waisted all
this money to setup the ultimate home network and i cant access video or
music from anywhere. there must be something simple i'm missing cause this
was so easy with XP and i cant figure it out in vista. thanks in advance