Simple fix .... trash the XP.
Sorry but I do not know about the webmin question. But in regards to SAMBA swat. It sounds like you haven't set up the /etc/inetd.conf file and the /etc/services file to enable the Slack box to startup swat on request.
The /etc/inetd.conf file should contain a line like the following:
swat stream tcp nowait.400 root /usr/sbin/swat swat
verify the path statement above.
The /etc/services file should contain a line the following:
swat 901/tcp # samba web configuration tool
They may be present but are remarked out. Then simply remove the hash from the front of the line. You need to SIGHUP the inetd daemon after the changes are made.
kill -s SIGHUP `cat /var/run/inetd.pid`
From the workstations, attempt to bring up swat using a normal browser by using the link to the Slack box IP address on port 901.
for an example.
Personally, I have never really liked swat because I thought it was too high of a security risk. But most, if not all, of my SAMBA installs are on server / gateways. I maintain the files from a console prompt using emacs, either local or remotely using ssh. I have all remote type services turned off except ssh. If your box is a gateway, then make sure the smb.conf includes the options to restrict the smb access to just the ethernet interface in use for the local network.
bind interfaces only = True
interfaces = eth1
I do not know if it will restrict swat to the inside network only since it is started via inetd. If I recall swat also requires root level login access and the password is sent clear channel. If you have problems with root login then you might check the /etc/securetty file to see if enabling anything in there might allow it.
Perhaps it will help some.