[TippeX]

u mean to do a copy from 1 dvd unit to another ?
if so then its pretty obvious you need 2 burners...
nero can do it - dvd copy or cd copy - u just make
one unit the source and the other the destination

if its protected you have to take other steps...

also probably worth mentioning that both units
have to have the same media..
ie: cd->cd = fine
dvd -> dvd = fine
cd -> dvd = nope
dvd -> cd = nope (obviously, considering the size difference)