To give you some background info which may assist finding further info regarding this and/or any future searches for info. TurnKey Linux is based on (and binary compatible with) Debian (v14.x = Debian Jessie). This means that any instructions for Debian (Jessie) should apply directly to TurnKey (v14.x). Ubuntu is another common Linux distro which is also based on Debian. So often Ubuntu instructions are also helpful and useful. However, please be aware that Ubuntu and Debian/TurnKey are NOT binary compatible. So to maintain stability, please avoid adding Ubuntu repositories to TurnKey servers or installing software explicitly designed for Ubuntu. As a general rule, all the software you should hopefully need is provided by the Debian (and/or TurnKey) repositories.

Regarding your use of Win98, I won't go on the usual rant about running really old and insecure operating systems as I assume you are already aware of that. (Win98 hasn't had security updates for MANY years and is highly vulnerable to attack). I'm guessing that you have some specific software or hardware that requires an old Windows version to function. Having said that, I would certainly encourage you to consider updating to a supported OS (perhaps a minimalist Linux distro?) if at all possible.

Anyway, back to the issue at hand... My brief googling suggests that Samba (the Linux software that recreates the Windows file sharing functionality) on our fileserver defaults to NT password hashing or higher. That is only supported in Windows NT/2000 onwards. Apparently Win98 is only capable of using the much weaker "lanman" password hashing (which incidentally is quite insecure).

So in theory, you should be able to configure Samba to allow "lanman" hashed passwords. I haven't tried it, but according to a post I found on the Ubuntu forums you should be able to configure the fileserver to allow it like this:

   1. Add these three lines to the [globals] section of your smb.conf:

      lanman auth = Yes
      client lanman auth = Yes
      client plaintext auth = Yes

   2. Restart the Samba server
   3. Re input passwords for every Win9x user:
      smbpasswd -a username
   4. Have every Win9x user log out and then log in again

Personally, I'd do all that from the commandline, but if you're not that way inclined, you should be able to do that within Webmin. From the top bar, please select "Servers" >> "Samba Windows File Sharing". Then click "Edit Config File". Make the changes as noted above, then click "Save". That should take you back to the main Samba page.

Then for point 2, scroll down to the bottom and click "Restart Samba Servers". Step 3 should also be possible via Webmin, I suggest you click "Samba Users" and attempt that there.

Good luck with it all. Hopefully that helps.