Computer won't boot when combo drive added.

Hello. I just got a new used computer (3 yrs old). It only has a cd drive so I'm trying to switch it out for the CDRW/DVD drive in my old computer. When I make the switch the computer won't start. Nothing appears on the monitor. The only thing that happens is that the combo drive spins a few times and it will open and close.

I've also tried unplugging the power cord and holding down the power button to drain the power with no results.

Anyone know what's up?