How much do you know about linux? There's lots of linux out there, many distros to choose from. Most distros support Live USB, so you can actually boot and run the entire OS off a USB flash drive - it's not a bad idea to try several different distros out before actually choosing which one you'll properly install onto a fixed system drive.
Linux Mint is a good distro for beginners. You should of course install some sort of dual-boot or multi-boot so that the user can choose which operating system boots up each time (linux, Windows, etc), and many distros (like Mint) include the needed bootloader software in their setups.
Most linux distros are built on the same operating system "core" (
kernel) then differentiated by software add-ons, extras, configurations, and extensions. The differences between major linux families often amount to their policies about legal/licensing details, version control, and package management. Some distros strictly maintain fully open source development on single every line of code, a few distros are fully commercialized, most distros fall somewhere in between to allow some balance between open collaboration and private development. Some distros focus on fully stable and debugged OS components which have proven themselves over rigidly controlled periods, other distros embrace the latest-and-greatest new betas, most fall somewhere in the middle. Package management is basically whatever mechanism is used to install and uninstall things along with "software update" functions and a sort of "app store" for getting more (free) software - different distros implement such stuff different ways. And there's always distros inspired by some individual or team which has decided to dev some flavour of linux "perfect" for their specific purpose(s), most of these rogue distros amount to little but now and then they evolve into large linux communities of their own.
Linux vs Windows:
most linux operating systems are completely free, there are never any hassles involving product activation or software keys locked onto specific hardware
most linux software packages are completely free, there are linux equivalents for every major Windows commercial software product
linux is actively and aggressively supported, millions of people code linux (for love), but only thousands of people code Windows (for money)
linux operating systems and software packages have been compiled for multiple hardware platforms, it's easy to migrate all your stuff between PC and iOS and Android
linux can run almost all existing Windows software through emulators (like WINE)
linux supports a wide variety of file systems, Windows basically offers only one (plus the few early versions needed for compatibility)
linux has limited DirectX support (many people are always working on porting DirectX but Microsoft owns DirectX and doesn't allow their proprietary code to be duplicated, and existing DX emulations/workarounds are too slow to provide impressive DX performance in games)
linux doesn't (and never will) have a whole lot of awesome games, especially not FPS-based games, game devs focus on Windows (and DirectX) because that's where all the money is
linux is not supported by all hardware manufacturers, some devices just don't work properly on linux (many people work on this too, but it's more hit-or-miss)
Don't be discouraged or prejudiced by "free". It's still "professional" grade, slick, clean, elegant, efficient. In many instances the "free" softwares are actually better than counterparts sold by Microsoft, Apple, Adobe, Corel, etc.
Some Windows-to-linux users are confused by the interface. Windows is all built around a single GUI embedded in the OS, it's organized the way Microsoft designed it to be and can be user-customized only in ways Microsoft allowed it to be. linux doesn't strictly have a native GUI, but these days every distro provides several GUIs to select from, and sometimes distros organize/customize their GUIs in ways which look wildly different from each other. Customized in ways far, far more than just changing desktop background, icons, cursor animations, and where the taskbar sits. Don't be confused, just navigate around and figure out what's where, an easy learning curve, no more difficult than moving from Windows to new GUI on a Mac or a smartphone.
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