Take it into the set up room and open the hierarchy editor.
Select an IK chain.
Hit the delete key.

Thats it :)

Sounds like it should work in the Pose room but I found that was not always the case so I use the set up room.

Then because you have gone into the set up room Poser may create a new OBJ file for it, if so just edit the CR2 to point back to the original.