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If you have documents that you want saved, back them up with anything else that needs saved.
You can then press F11 on startup repeatedly which will get you into the recovery menu screen, from here we can restore it to factory default and it will appear as if it was brand new out of the box.
Everything would be wiped and reloaded as if it were preloaded by Lenovo.
Did you purchase it straight from Lenovo or something like ebay?