Well if you are wanting to go back to a version prior to the installation of 10, you may need to obtain CDs/DVDs/USB with the OS you want on it.
You can also try downloading the correct version here... https://www.microsoft.com/en-us/software-download ...but there is no guarantee it will work for you. Sometimes it doesn't if you don't have the right product key.
I have been using this laptop and has never failed me, until they automatically installed windows 10
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