How to factory reset a computer without the password?

So my friend sold me their Lenovo desktop computer a few days ago; I believe the computer has Windows 8 although I m not sure. It s in great condition, there s just one problem: they never reset the computer. So, it requires a password to get into it. They told me it should ve been reset but they think maybe it didn t work. And they don t remember the password, which is great. I have seen a few suggestions on starting the computer in safe mode. I held f8 while booting up and nothing happened. I don t have a software disc or anything like that, nor do I have another computer at the moment to download something onto a USB or disc for my new computer. I know, not giving y all much to work with here. But I would very much appreciate any help I can get, or if I am starting safe mode wrong please let me know! Thank you everyone!

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