How to completely wipe a computer clean/reformat without disk

sunnylove

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Aug 3, 2015
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Hi!
*waves*

Im sure this question has been asked various times so i apologize in advanced.

Im moving to a different country and am selling my computer to a buddy of mine, i had windows 8 on it and I would like to reformat the computer for him to make it nice clean shiny and new.
I have all my product keys but no disks... Im wondering if this a problem?

the computer is only about 6 months old. but still would really prefer to wipe it clean and reformat it?

If anyone can help me that would be great in the simplest terms possible please