Vista - Networking Vista with XP

I currently have a home network with xp and my machines have all updates and
am currently running SP2 on them. The main PC is hard wired to my router and
everything else is running wireless.I just recently purchased a new notebook
that has Vista home premium and tried to network to my existing network but
kept having errors saying I need to ask my administrator, well I found out
that microsoft came out with a patch to fixthis problem because vista is
running a different networking protocol than xp, so I installed this patch on
my XP machines but still came up with same error.

I let it go for a few days because I got tired of messing with it and the
next thing that I know I tried to access one of my pc's and instead of
getting the error I get a pop up box wanting a user name and password to
access this pc. I really don't know what user and pass that it wants because
I dont require any passwords on any of my pc's so I thought maybe I should
make user account with passwords on my pc's and then type that in the box but
it still doesn't work tells me that wrong user or password.I don't have any
personal firewalls nor am I running MS OneCare or any other 3rd party
firewalls.Any info would be greatly appreciated.