network log on screen?

I just reloaded XP on my main system which serves as the
internet connection "host". From the client computer I
can connect to the internet through the network but when I
try to access files on the host a little box pops up
asking for the client to enter user id and password. This
didn't happen before the reload.
How do I remove this? I have set up the host drive and
folders to "share" already.

Thanks,
David