I heard that Duplicate objects still share the same mesh. I need a way to completely separate the duplicates from one another. Help?

If so, you can select your duplicate and choose ‘make single user’

And how would I do this in Blender 2.49b?

I don’t understand the question I guess - I have 2.49b open, and when I use shift-D, I get an unique copy ,except for the material being common. I solve this by pressing the number next to the material name, to make single user there. Alt D would have made a linked copy instead, at least from the menu under Object I get that.

with the object selected look in the object menu