On Secondary, should it be LiteOn DVD master then NEC 2510 or NEC 2510 master and Liteon dvd slave
It should not matter as long as they are not both master or both slave.
it wont matter where you place them as long as they are master and slave. put one on master and one slave or put both to cable select and it should work.
Cable Select would be best for most systems.
ARghhhh nooooo did i hear those two words together 'cable' and 'select'? a word of advice dont do it, if your running 80 wire cables set the end of cable drive to master and the central drive to slave. sorted