If you mount a blower in the case, don't put it near to the optical head or drive spindle. Fans will cause dust to collect and that will shorten lifespans. Put it near the rear of the box, sucking air out of the case. You may also need to consider making holes to let air into the case, the same precautions apply. You'll also find 12v fans and blowers at R.S., get the lowest airflow you can find.