*wonders : " a little too technical for that board ?" *
@ Bizon :
You might be having problem with your de-PBO tools. I've read somewhere in the official forums that you shouldn't use de-PBO, but Un-PBO.
Careful, though : use Amalfi's LATEST unPBO, because mine was too old and some files just couldn't be read by Visitor (yes there are several around).
Anyway, the "O" add-on contains several directories : Anim, char, guns, hous, trees, music, etc.
Just put it -unpboed- in your buldozer folder, and target it in your system preferences
(especially for the artificial and natural objects).
That way, when you want to add roads, trees or houses, it'll be clearly indicated in the dialogue box (tree\DD_bush02.p3d). That's it.