If you have installed Windows 10 free operating system you can still install Linux on your computer. Linux can be run simply from a USB drive without even the need to modify the existing system.
Here are the things you need to remember.
1. A "dual boot" system for installing Linux distribution alongside the Windows will provide you with an option of using either of the operating systems each time when you start up your PC. It is an ideal way to install Linux, as that way you will always have the chance to get back again to a full Windows system just with a single reboot.
2. If you are going for a dual-boot, what should be of primary importance is to install Linux on any system preferably when Windows has been already installed. So, if your hard drive is empty, first install the Windows, then the Linux.
3. Then follow these steps:
a) Choose the Linux distribution.
b) Download Linux and create a USB installation media or simply burn it to a DVD.
c) Boot the Linux Os on a PC that is already running on Windows.
d) After launching the installer follow the instructions.
e) Now choose the option that says 'install the Linux system alongside Windows', or you can even opt for the manual partitioning and yourself create a Linux partitions along with the Windows.
f) Never choose the overwriting option of replacing Windows system with Linux. Otherwise, your system can be messed up, and if you feel like going back to Windows, it would be a laborious process.