If you have Poser 5 you could use the grouping tool to
select just the boots and create a prop from them.

Go to Editing Tools. The Grouping tool is the 4th one
from the right, the box looking thing with a dot in the
middle.
Click it and a dialogue box pops up. Everything goes
gray. Now click on an item and it turns red. So click
on the boots. Use the - sign to remove parts you don't
want and the + sign to add them back if you removed
the wrong part.

Then in the dialogue box click Create Prop.
You should now have a duplicate of a boot which you can
save as a prop. Do the same thing for the other boot.