Let's Begin with a few things: WINDOWS XP: This OS may be efficient but is quickly becoming obsolete due to windows 8, but Windows 7 is even MORE efficient and has a LOT more support!, it's faster and more reliable in the long run as long as you keep it current!!, if you own an old PC, and it has a 1GHZ CPU, slam a gig of DDR400 in there and bash in a GeForce MX 420 GPU, then add windows 7 to the mix and you have a bottom of the line PC that is good for day to day tasks like surfing the web or playing minesweeper!!, not only that but the debugging and overall health of your system is more advanced and the PC will have an easier time running it! WINDOWS VISTA: WTF are you still doing with that OS, it's taking ALL of the resources you could be using for games or someyhimg like that but instead, all that memory is being wasted on the OS, you can't even tun minesweeper straight unless the system you have was soully based on gaming!! LONGHORN: The follow up to vista: less resource hungry and has no support as this OS was not officially released and I wanted it and can't find an ISO anywhere, but, it would have made life so much easier than Vista, I mean, WHAT WAS BILL GATES THINKING!!!???