How do I bypass the administrator password

Okay. So there seems to be 2 different questions going on at the moment so I will address both to the best of my ability.

If there is a password required as soon as you turn the computer on, the previous owner put a password on it in the BIOS. You can try to get into contact with the person who sold you the computer and see if they remember the password, or another thing (which I'm not sure if it'll work or not) there is a circular battery on the motherboard of the computer. You can remove that, leave it out for a little bit (30 mins to an hour) put it back in or put a new battery in, and see if that resets all the BIOS settings or not which in theory get rid of the password. Don't quote me on this though.

If the OS (Operating System) cannot be found, that means that the hard drive has been erased prior to you buying the laptop, or the hard drive is damaged. However, this isn't too terrible. If the hard drive (HDD) has been erased, all you have to do is get a Windows Install Disk or ISO file, which the Windows 10 ISO file is available on Microsoft's website. Burn the ISO file to a CD or Flash Drive (instructions can be found online or I can provide them if needed). Then take the freshly burned ISO USB or a Windows Install CD and put that into your laptop. Install Windows. Good to go.

Another option. If you don't feel like using Windows or buying a new Windows License Key or whatever your reasoning is, you can also download and install a Linux OS, for free. There are many different Linux OS' however and if you are not familiar with them I would start with a simple one like Ubuntu or Mint. They can be downloaded and put on CD or USB and are 100% free and legal. Great for updating an old Desktop or Laptop.

If nothing happens or the computer says the OS cannot be found still, make sure you change the BIOS settings to boot from USB or CD. If the same message appears, you will most likely have to get a new hard drive. However, you can get a faster hard drive called a Solid State Drive (SSD) which will speed up your computer significantly. You will need to install Windows or Linux regardless of what you do though.

I hope this helps!