How is the new drive installed......as the master on the second IDE channel or as a slave to the hard drive?
If it's the latter make sure the jumper settings on the dvd drive are set to slave(If the former set them to master).
Make sure the power connector and ribbon connector(red wire nearest to power plug) are fitted the right way round and fully inserted.
If still no success then boot into the BIOS (tap delete on startup) and see if the new drive is listed in the basic BIOS settings........If not it might be faulty.
The easiest way to check is to try it in another pc if you can.