If you cannot , or will not use swat, then at least run testparm against your config..
Right off the bat you have no workgroup name,so windows
boxen cannot and never will be able to connect.
In global assign the workgroup the windows machines are
in.
Previous post was right also in that you need to enable encrypted passwords.
Running testparm and saving it to a text file will give
you all of the available settings so you can look
through and then fix what you need to in smb.conf.