It's just as easy (and tidier) to replace the internal DVD drive.
Google for 'how to replace a dvd drive in a desktop' for a video walk through.
Also have you checked that the dvd drive is actually broken (can't read contents of CD/DVD's? Look in Windows Explorer and click on the drive to see if the contents are shown or if it says 'drive empty' 'please insert cd/dvd' or similar message.
It might even be just a loose connection at back of drive, make sure they are firmly plugged in. (pc switched off and unplug from wall socket when you do that)
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