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Enter your v8 key in the Macrium Reflect download manager. Your v8 key will begin with 76-, 77-, 78- or 79-.
If you got an existing v7 install then there's no need to download, just take the 'Other Tasks' > 'Check for updates' menu option and follow the prompts.
Please see Installing a Macrium reflect v7 to v8 Upgrade
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