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If the computer could connect to the internet and is a modern operating system, install the appropriate software on the computer in question and follow the imaging and transfer section. (link)
Remove the hard drive from the computer and connect it to a processing computer, following the steps above for in the relevant hard drive above hard drives and storage devices section.
Turn the computer on and connect it via its external ports to the processing computer and transfer the files following the appropriate imaging and transfer section. (link) Some computers have a specific transfer mode, such as Target Disk Mode for Macs.