Ho ! right... then look at the back of the DVD rom... there is a jumper..

it may be on the left hand side it looks like 4 prongs with a small collar on..

you cover the prongs with the collar.. and it only covers 2 of the prongs..

for the "primary" CD/DVD rom (that's the main rom) you should cover the the 2 pins on the right hand side with the small collar..

for the "secondary" CD/DVD rom (that's the one you have just put in ) you should move the collar to the middle 2 pins..

use a small pointy pair of pliers to move the collar...