That's what I said ST, you plug the normal map into the gradient bump channel, the only problem is you don't get the option to change how the map is used, in later versions you get 3 options below the Gradient Bump channel called Gradient mode, Gradient Bump, Normal map (Tangent space) and Normal Map (Object space), as bagginsbill said, it probably won't work quite as you expect in 6, since the normal map really needs to be set to Tangent space to work correctly, I can't remember which prog you use for your modeling, but if it's anything like LW or C4D, you can load the normal map in those and render it out, that'll give you a good idea how it'll look in the newer versions of Poser, there's always a slight difference because of how each prog sets the power on the map, but not much that'd make a big difference.

 

If need be mate, pass the model and map over and I'll do a test in P7/8 for you, send you back a render so you can see how it looks in both of them, PM me over at PDF if you need a hand

 

Billy