I want to clone so I can keep my original in pristine condition and use the cloned DVD in the computer.
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You do realise DVD readers are a laser based non-contact medium ?
You do realise that DVDs are NOT an investment ? They are a mass-market commodity product !
Anyhow, copyright issues notwithstanding, in answer to your question. Create an ISO image of the DVD and burn it back. Any half-decent CD/DVD writing software should be able to cope with that.