According to this article:
Windows 7 has finally surpassed Windows XP as the most popular desktop operating system with a 42.72% market share. Windows XP at trailed only slightly at 45.52%. Windows Vista held 6.15% and various Mac OS versions totaled about 4.83% share.
It comes as no surprise to me that XP still dominates over Vista as nearly everyone I know either skipped that version or switched to Mac or Linux after growing frustrated with its numerous problems. I have used Windows 7 in a Virtual Machine under Linux for several months now. I’ve generally been pleased with it and I’ve had no problems serious enough to lead to premature baldness. If you’re still running XP, it’s time you considered making the switch to Windows 7 or perhaps Windows 8 when it is released in late October. If you’re more adventurous and want to keep your old hardware you might want to consider trying one of the new Linux distributions such as Ubuntu or Linux Mint. If you’re tired of Windows and have some cash to burn maybe now is a good time to get a new Mac?
Whatever you choose, I urge you to act sooner than later since Microsoft’s extended support for Windows XP ends April 8, 2014. After that date Microsoft will no longer provide security updates and bug fixes for Windows XP. I recommend that you plan to be completely done with XP long before the EOL (End of Life) date for all of your main production computers that are connected to the Internet. Unfortunately, some of you will most likely have certain critical legacy applications that only run in XP either due to compatibility or licensing issues. In those cases, I recommend that you experiment with running the legacy applications in a Windows XP Virtual Machine under a newer OS. If the VM (Virtual Machine) approach works you should be able to choose whatever newer OS you like (Windows, Mac or Linux) and still have the benefit of the older software. If the VM approach doesn’t work then I suggest you plan to isolate your legacy Windows XP computers from the Internet to help avoid exposing them to whatever new threats might emerge after the EOL date.
The next 18 months could be some of the most interesting times in modern computing history. In that short time we’re going to see some 40% of the world’s desktop computers either retired or switched to a new operating system. No matter how things turn out the market opportunities that exist now may never be repeated.