How can I reset and align bones? My question is quite easy and straight forward.
I'm rigging a low poly dog I modeled in order to give him a "pose" before rendering. My problem is that once created the bones for the right part of the body I duplicated them to the left part of it in order to to avoid to re place them one by one. The paws [front and back] of my dog point to an external object [null] in order to avoid to have them always parallel to the ground.

My problem is that once duplicated them the paws of the other side still point to the pointers of the right side. I tried to duplicate them and link to the bones of the paws but nothing happens.

Is there a way to "unlink" the left paws and "relink" them to the new pointers?
I'm adding the bones I created in order to make my explanation a little bit more clear.

Thank you in advance for your help
Ciao to everyone!

P.s. I uploaded the file on 2shared.com in order to make it accessible to everyone.

http://www.2shared.com/file/gKR5AgUL/bulldog_ricomincia_zampe.html
If you select in edit mode a bone whose "pointing" you want to change, you should be able to go to the tab that looks like a single bone in the Properties panel. Then, under Relations, go to the Parent: drop down menu, clear the current parent, and select the new desired one from the list. Repeat this process until finished.

I used this website when learning to rig. There are many good pointers on it.

Update:

To answer the question in your reply, select the offending foot, and go to the Bone Constraints tab in the Properties panel. Where it says punta_zampa_ant_dx, click and change to punta_zampa_ant_dx.001, the other empty. Repeat for the other offending foot, but select its empty instead of punta_zampa_ant_dx.001.