Setting up Samba so that you can use your Linux-based machine as a fileserver for consumption by a Windows machine is not trivial.
Samba Setup Guide For Linux – this is probably the best page – a nice walkthrough, that worked pretty well for me, up until the last point (restarting samba was “/etc/init.d/samba restart” not “/etc/rc.d/init.d/smb restart”)
Ubuntu wikipage SettingUpSamba
I also think that this forum thread on MandrakeUsers and this one on Techspot have some useful notes.