Must replace two PCs with N360

I have a 3-seat copy of Norton 360, and have to replace two PCs (one an XP and the other Vista).  The new PCs are both 64bit Windows 8 machines, and each presently has an evaluation copy of Norton Internet Security on it.

What will be the best way to ensure that I clean Norton Internet Security off of the two new machines, and that I can efficiently transfer the two copies of Norton 360 from the old machines to the new?

Thanks in advance!

Tom