print share with vist and XP

Hi,
I'm having problems connecting to a computer to access the shared resources
on it, like the printer and folders. Here are the details below.
Two computers one with vista and the other with XP. The Vista computer can
see the XP computer but will not connect to it. it will ask for a username
and password then when you put in the correct username and password it says
its not correct. The XP computer can conect to the vista fine. Any ideas
would be great.
Thanks