At this point, Linux installers should be fairly mature and capable of resizing Windows NTFS partitions without breaking anything. But it's essential to always have backups of your important files in case anything bad happens. Of course, the Linux installer will only be able to resize your Windows partition to make room if the Windows partition has a decent amount of free space on it. If you have a PC with multiple hard drives, you could also just leave Windows installed on one hard drive and install Linux on another separate hard drive. But they're perfectly capable of living alongside each other on separate partitions on the same hard drive.
Choosing your operating system and sharing files
Switching back and forth between operating systems is simple. Just reboot your computer and you'll see a boot menu. Use the arrow keys and the Enter key to select either Windows or your Linux system. This will appear every time you boot your computer, although most Linux distributions will boot a default entry after about ten seconds if you don't press any keys. If you have a modern computer with a speedy solid-state drive, switching back and forth between Linux and Windows should be quick.
Linux gives you easy access to your Windows files, and you should see your Windows partition appear in your Linux desktop's file manager so you can easily browse and access your Windows files. Windows doesn't provide easy access to Linux file systems. Most Linux distributions use the ext4 file system, so you'll need a third-party utility that supports ext4 file systems on Windows if you want to access your Linux file system from Windows.
A dual-boot configuration is also essential for PC gamers who want to run Linux. Whenever you encounter a game that only supports Windows, you can just reboot to play it in Windows with maximum performance--no tweaking necessary.
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