Caligari truespace is an excellent program to learn first. It is free and it is a very good program with lots of functions, but most importantly there are also a lot of free downloadable video tutorials on the site as well that teaches everything about truespace.
Blender is a powerful program as well that is freeware, But unfortunatly it tends to scare people away cause it has been considered to have a high learning curve to it. Personally, I've had a go with blender myself. Really, although I don't use it and like truespace more. I did'nt find it that hard to learn, I just don't like the layout. And blender has tutorials as well just google them.
On a side note though, If you plan to use these modelers mainly for Dark basic pro, The two that I have mentioned are probably about the most advanced and most importantly "compatible" 3d modelers you are going to find on the net that is freeware.
most modelers are compatible but usually through external programs for converting.
And last I recommend these modelers for four reasons TUTORIALS/ COMPATIBILITY / More ADVANCED than any other FREEWARE and well shareware 3d modelers out there. And the best part of these they are professional and FREE And loaded with tutorials that are easy to find.
By the way what is EASY? what maybe easy for one person could be very hard for another.
WindowsXP/SP2, Pentium 4 2.66 GHz, 1GB DDR Ram, Geforce 6600 256MB