Ah crumbs! Please put a warning when an adult link like that is concerned. I'm fearing my bosses are going to think I'm a right perve - which I am but I don't want them knowing it ;D
What about trying this post from Awasson (there's also one from Moondog somewhere) & remember to adapt include/categories.php (which makes subcategories available)
http://forum.x-cart.com/showpost.php?p=161471&postcount=37
The whole thread...
http://forum.x-cart.com/showthread.php?t=13345
Hope this helps.