Download rufus (https://rufus.ie/) Download a Linux distro, for example Ubuntu: https://ubuntu.com/download/desktop/thank-you?version=20.04.2.0&architecture=amd64 Write the ISO to a USB with rufus Boot from the USB and install Ubuntu to your HDD (this will overwrite all your data on the disk) Done! (There are plenty more in-depth guides online)
1. If the disk is big enough, use windows disk management to split the Windows OS and the data each into their own partition. If not, backup your data elsewhere. The data are normally in user-name/all-main-data folders but they can be elsewhere too. 2. Install your preferred linux on the OS partition if you no longer need it, or to the whole harddisk. I would prefer to clean and properly partition the harddisk before installing linux but as @Th0m said above, more in depth sort of guides are needed.
