is the old for trashed/bent? will it be going to the recyclers? if so, you CAN reuse that star nut! simply cut the steerer tube BELOW the star nut, then drive it out of the tubing.... i install the star nuts by using a socket that is smaller than the steerer tube, and a socket extension, then make sure the socket/extension is in line with the tube. and drive it down into the new fork to a depth similar to the previous installed depth. DONE
or, do like the previous post says, and go get another star nut.
where i live, the nearest supply of new star nuts is either my stock, or an hour's drive, during daytime traffic, so re-using is a better option when i don't have a new one here.