[LDiCesare]

It's not white borders, it's white pixels, one per province. And you have to place them by hand where you want the province to be.
You can, on the other hand, draw red borders between provinces in order to help Dom guess the neighbours.
That's quite ugly-looking if you keep them, however (even by my standards) so it's better to put them in a layer if you want to use the help and save 2 tga's, one with the red borders and one without. However, even the red borders stuff doesn't help that much and I usually do all province neighbour placement by hand anyway.