How to enable file sharing?

On WinXP Pro, when not a member of a domain, this OS flavor enables
something called "simple file sharing".

I have a computer running this configuration. When I right click a folder
and bring up the sharing tab I see a message that says I need to enable file
sharing. I have a choice to run a Network Setup Wizard, or enable this on
my own.

How do I do this enabling programatically? Because if its not set and I use
NetShareAdd, the share is not accesible by a remote computer. I found no
registry changes that were made my enabling file sharing in this mode. And
please note that File and Printer Sharing is enabled in the network
properties. Somehow this switch is different.

I need a way to either: detect that the system is in this state, and/or turn
on file sharing capabilties if it is not turned on already.

Configuration is a clean install of XP Pro, configured as a stand alone
computer (ie. not part of a workgroup or domain).

Any help would be much appreciated.

Thanks!!

John