I was thinking of getting XP, but after April MS won't have tech support for it. And fallout 3 isn't optomized for windows 7 : (
Wut why would you get XP? I never understood the love for it.
Get Windows 8.1, install Start Is Back and be happy.
Or Get Windows 7 and also be happy/happier depending on who you are.
Also there are tons of Linux Distros out there but of course there are many more games on Windows than Linux although that is beginning to change.
Personally I prefer Windows 7. I myself loved XP and if they still had support I would probably still use it. That being said my Windows 7 rig runs Fallout 3 without a hitch.
It really depends on the gaming you want to do. Most games that come out (and avoid being locked to some DRM lockbox of a console) will be playable on Windows. Choose that if you want "all the games!". If you are willing to dig about a little, you can get a type of game for whatever you crave in Mac OS X or Linux. If you want professional support and an exceptionally proficient OS, it comes down to your hardware. Mac OS X generally has great performance for whatever hardware they initiated into their world of Apple, but will refuse any "commoner" pieces. Linux will generally let you scrap up a machine with whatever you have lying around that can be shoved together, but will give you trouble with proprietary graphics drivers (if you decide to go down that route) or NVIDIA cards as the open-source Nouveau driver is notably behind the closed-source NVIDIA and open-source AMD driver.
You want to play any specific game? Windows
You want to play any kind of game on any kind of hardware (expect lower performance or compatability issues from NVIDIA products)? Linux
You want to get an OS that's considered more "professional"? Mac OS X
You could also try BSD and other Unix-related OSes, but those usually sit next to Linux.
- Use Arch Linux, Sabayon or Manjaro as your primary OS.
- Use Wine/PlayOnLinux to play older games natively on Linux.
- Virtualise a Windows OS to play AAA games with VGA passthrough.