Cannot access share from machine that is part of a domain.

I have a machine in a lab that is not a member of a domain, just
"workgroup". On this machine I have a directory below the root that is
shared with full control to everyone. The directory permissions are
also set this way. I can access this share from every machine in all
the labs, the common theme being they are all non-domain members.

However, when I go to a machine that IS a domain member and try to
connect to the lab machine, I am prompted for a username/password. The
goal here is to have a batch job running at night copy files into this
share, but it can't because it is running on a machine that is a domain
member.

Thank you,
Jim