The answer to this question may vary depending on the type of computer that originally contained the DVD-ROM drive. If the DVD-ROM is inside an external USB enclosure for older laptops, then it seems likely that at least one auxiliary device no longer works and is preventing power from reaching the DVD drive. Power connections or power regulators can also be faulty, or there could be a short circuit. Furthermore, if the DVI/HDMI port was plugged into an input card with old video drivers incompatible with modern CPUs (the case for most Atom N450s), then you will need to upgrade your graphics driver before connecting it to a monitor again.