Pjiang or XiaoBaitu, Please help!

Pjiang or XiaoBaitu or any experts:

Can I file second 485? I already filed EB2 1-140 and 485 concurrently in Nov. 2006. Now both I-140 and 485 are pending in NSC. I have another EB3 I-140 approved. Can I file another 485 against this EB3 I-140? If so, how can I do it? Do I have withdraw the first one or can the two 485 go parallel? can I switch the first one to the second one?

Appreciate your help! Thanks a lot!