Rob,
My fstab has:
//pcname/pcsharename /mnt/backup smbfs username=name,password=pass 0 0
I've had no problems connecting to a Win2K box either. The account and password need to be for the domain, not a local workstation account, FYI. I was using my own userid/password, as my account has (local) administrator rights.
HTH,
Des