We can't answer that question, and no I am not suggesting that you download a pirate copy of it.
I'm merely saying that if you are asking about buying Windows, then you probably aren't experienced enough to use Linux, as Linux is a whole new world and would require you to learn a great deal before it would be as usable as Windows is to you now.
But to answer your question "is linux hard to use? and can things that require Windows XP SP2 (like hardware and games) be run on linux?"
At first, Linux will be difficult to get used to, but once you're used to it, it can be a lot easier to use than Windows, and you will never want to turn back to Windows. Some things that require Windows (such as Windows programs, what have you) can be run in Linux using Wine, or Wine derivatives such as Crossover Office or Cedega. In my experience, 1 in 5 games I try to play in Cedega have worked well. The others either didn't work at all, or worked very poorly. There are native Linux games as well, such as Doom 3, Quake 4, UT2004, Return to Castle Wolfenstein, Wolfenstein: Enemy Territory, and soon to be Enemy Territory: Quake Wars, and UT2007. The reason these games are able to be easily ported to Linux is because they don't use DirectX rendering, they use OpenGL. These games work just as well as they do in Windows, if not better.
Linux works on 99% of the computers out there including Macs, cell phones, iPods, and regular PC's. Almost all hardware is supported, including newer video cards and even SLi multi-GPU rendering. ATi's video drivers are pretty flakey in Linux, so if you use Linux I suggest an Nvidia card, as my experience with them in Linux has been nothing but excellent.
If you would like more information about Linux, post in the Linux section, you'll get tons of useful links and help if needed.
Oh, and one more thing: Linux is free (free as in beer,) you may download it, burn it, and install it free of cost, and 95% of the software out there for it is free. There are Linux alternatives to all
Windows software, and most of them are free.