sudo apt-get install samba
sudo apt-get install smbfs

sudo cp /etc/samba/smb.conf /etc/samba/smb.conf_backup
sudo gedit /etc/samba/smb.conf

Find this line

workgroup = MSHOME

Replace with the following line

workgroup = new_domain_or_workgroup

Save the edited file (sample)
sudo testparm
sudo /etc/init.d/samba restart

Linux itself doesn't use workgroups like Windows does so you need something like Samba to allow Windows and Linux to operate in the same environment.