[D Brugge]

Agreed that that is the usual way to go, but it's not ideal. An ideal solution would be for X-Cart to allow the full incorporation of WordPress into its framework.

But since both X-Cart and WordPress rely on cookies to keep track of who is logged in, there seems there could be a solution, as long as the user name, etc match. It seems that you can turn off registration in wordpress and perhaps write a script that uses the new user email feature from x-Cart to register a matching user for Wordpress. Then, when a user signs in to x-cart, generate a Wordpress session cookie as well.

As far as being able to register at one and have it passed to another, that's a much bigger hurdle that involves security problems. I'm only wishing out loud on that one.