OK, it sounds like you'll need to format the drive and start fresh. You'll need either an install disk or flash drive, which you can make yourself so long as you can use another PC. A copy of Windows 10 can be downloaded from here:
https
/www.microsoft.com/en-us/software-download/windows10
The media creation tool in the link can make an installer from either a blank DVD or a flash drive (min 4GB). It can be activated with the key that came with the laptop: if the laptop has a windows 7 sticker on the bottom you can enter that when prompted, and if it came with 8 or higher the key is embedded in the system and Windows will automatically read it.
If you're able to make an installer, pressing F12 at bootup will give you a menu of...