$ sudo apt-get install samba

Edit config

$ sudo nano /etc/samba/smb.conf

Replace with this simple config. Don't forget to create your share directory.

[global]
workgroup = YOUR_WORK_GROUP
netbios name = YOUR_COMPUTER_NAME
security = SHARE
auth methods = guest
domain master = No
wins support = Yes

[Sharing]
comment=My Ubuntu
path = /home/your_home_directory/Sharing
read only = No
guest ok = Yes

save, exit nano and restart Samba

$ smbd restart

done

Mount folder from XP, Vista (share folder from XP, Vista)
Install smbfs, smbclient

$ sudo apt-get install smbfs smbclient

Edit auto mount

$ sudo gedit /etc/fstab

Add your target share folder like this. Don't forget to create your mount directory.

//192.168.1.1/Sharing /home/your_home_directory/Vista-Sharing smbfs rw, 0 0

//192.168.1.1/Sharing = Your XP, Vista share folder (test by type \\192.168.1.1\Sharing in Windows location bar)
/home/your_home_directory/Vista-Sharing = Directory in your Ubuntu

Re mounting device

$ sudo mount -a

done