Change of Name in my Acer desktop

Hello to everyone:) I hope someone might be able to help me! I have purchased a great Acer destop from my daughter it is fantastic and modern! BUT! So many things are in her name Documents ,Computer lots of files, I try just to put my own name in but hers stays in there too, ( well actually it is her ex partners name ) I just want to get rid and replace it Can anyone help I have tried all the simple silly things, Help please if you can? Thank you so much. :)

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If it doesn't kill you it only makes you stronger! or so they say!!:)