Most PCs are being sold with Windows pre-installed and so many people probably never even thought about such a question as 'Do you really need Windows?'. Here on GD where most of us are using PCs for heavy gaming or other demanding multimedia tasks, it probably doesn't make much sense to move away from something which works fine.
But let's face the truth, many people use their PCs and laptops for only basic tasks like browsing the internet, checking emails, playing music, watching videos, writing documents, viewing and editing photos... Maybe you'd be surprised to hear there are better operating systems for such purposes, less resource demanding, more secure, completely free... Yes, you're right if you guessed I'll be talking a little bit more about Linux-based operating systems.
(Linux veterans excuse me for writing Linux-based instead of Unix-based, but it's easier to understand for newcomers!)
At first, there are plenty of various Linux-based distributions (=distros). The best thing is each offers something slightly different and you can run them without installing anything - this is something completely unknown and incomprehensible for Windows users - basically you can download an installer ISO, and either burn it onto a DVD (CD sometimes) or make a bootable USB stick, and boot it up without installing anything - without modifying anything on your current disks and systems. Everything is running "live" from the source media and is loaded into RAM. Overall responsiveness may feel little laggy, especially with heavier Linux distros (most of which are still lighter than Windows), especially if run from ancient optical drive or very slow USB stick, but you can of course install them on your disk (I recommend separate HDD just to avoid any problems - if anything fails you can format it and start over again).
A crucial aspect about any OS is software compatibility and overall software offerings. Linux-based distros do NOT open .exe files at all, which on the one hand is an awesome sort of anti-virus protection, while on the other it means you cannot use all of the programs you already use on Windows. But no worries, there are alternatives to choose from and even some popular programs are offered for Linux-based OSes directly. And if that's not enough you can try WINE, which is a free software implementation of Windows inside Unix
Hardware compatibility is somewhat risky - usually any common device you have will work under most Linux-based distros. For common devices you don't need to search for any drivers because those are installed automatically, many of them are somewhat versatile, but shouldn't limit you on common usage. This is particularly great for older integrated audio cards, network interfaces and other legacy hardware where you may have unsolvable problems when trying to make them work in recent Windows versions (7 and newer, like Windows 10 especially). From my own experience, it's less likely you run into compatibility problems compared to Windows.
Which Linux-based distro to try then? Sly answer is that depends what you need. There are plenty of various distros available and if you really want the best, you need to check as many as possible to determine which suits you. Usually you seek for desired combination of core (affects available software install) and user interface (how the OS will look). To start somewhere, let me suggest a narrow list of my personal favourites:
Linux Mint (Cinnamon) - for Windows users, this one is easiest to understand thanks to a very synoptic user interface. If you ever heard the term "Ubuntu" then this distro is using its core, so you shouldn't have problems installing any programs designed for Ubuntu. Cinnamon's fairly stable so you really can't go wrong if you opt for this distro.
Ubuntu Studio - this one is probably the best distro to try if you want a fully-equipped operating system out of the box. Although it may look a little ugly, you can be sure it's because maximum performance is being piped to your tasks and not useless resource-heavy OS runtime applications. As written on its official site, Ubuntu Studio provides a full range of multimedia content creation applications for each of the workflows: audio, graphics, video, photography and publishing
Manjaro (KDE) - this is my personal favourite. Majaro's based on Arch Linux and NOT Ubuntu, which may be more confusing for beginners, but I really like the way you can "learn Linux" if you use Arch Linux. Its sleek design and customization options, together with a very wide range of supported hardware makes it the best choice for people who want to finetune the OS to suit their needs. Also since it's Arch-based, software is installed and managed slightly differently.
Steam OS (Beta) - it's Debian-based distro, so far in Beta stage. SteamOS is targeted primarily at gaming, which means it has Steam and maybe some other libraries preinstalled. To be honest it doesn't look as aesthetically pleasing or powerful as any of those distros I mentioned above, but I felt it really deserves to be on the top 5 distros list. After all, we're on Game Debate and this may become gaming operating system no.1 within a few years
Lubuntu - again based on Ubuntu, so it's the same core and same software repositories. If you have a really ancient machine and only want to read emails, documents and browse the internet, then this is the distro worth trying. The minimum recommended requirements (which are sufficient for regular use) are: 1GHz cpu, 384MB RAM (with 512MB and more you don't need to worry about RAM usage at all), and up to 800MB disk space (depending on what you choose during install)
Once you get the desired OS you need to learn Linux (free) alternatives for Windows-based software you've been using up 'til now. Most internet browsers such as Firefox, Chrome, Opera, Vivaldi etc. are provided natively for Linux-based OSes, with the only exception that Chrome is named Chromium. To replace Microsoft Office you can use LibreOffice (which is available for Windows, Linux, OS X), and it's totally free. For photo and image editing you can use GIMP, which is very popular even among Windows users, and completely free again. A VLC version for Linux is available as well. For vector drawing you can use Inkscape, which is free again. For editing music you can use Audacity, available for Windows too and again for free. If you need hardcore digital audio workstation, Ardour is what you should definitely have, free of course. For 3D modelling and video effects, Blender is what you can use, free again. For converting videos probably best is HandBrake, again for free. For archives, both WinRAR and 7-zip are available, for free of course. FileZilla is what you can use as an FTP client. Steam is available as well, you don't need SteamOS to have the Steam client on Linux. If you want to run a home theatre PC, then probably the best software to manage that is Kodi Entertainment Center, formerly known as XBMC, or Plex, of course both free again.
So what's the problem? Well, DirectX, MSVC (Microsoft Visual C), NET Framework and other APIs and libraries are Microsoft's monopoly, with publicly non-available source codes. So any games and programs which require these are likely not possible to run in Linux-based OSes. Another issue may be graphics drivers. Although manufacturers are providing drivers, the source codes are often unavailable and so it's up to manufacturer's goodwill to provide good drivers. As I wrote earlier, there is WINE, but it doesn't guarantee you anything. The best solution is to get a Linux-friendly version. For example on Steam there's a growing section of SteamOS+Linux games, some of them being free, many of them being paid. Among the top games are DOTA 2 and Team Fortress 2 (both free), but you can find also titles like Portal 2, The Witcher 2 and much more.
Are you using any Linux distro already? What do you think about Linux-based OSes? Are you considering a move from Windows? Do you think Linux-based OSes may ever rule gaming? Have you ran into any problems with Linux installation or other issues with Linux? Let us know what you think and don't hesitate to ask below if you need any help.