http://www.netmarketshare.com/operating-system-market-share.aspx?qprid=10&;qpcustomd=0

Windows 7 46.42%
Windows XP 31.24%
Windows 8 7.53%
Windows Vista 3.63%
Mac OS X 10.8 3.31%
Windows 8.1 1.72%
Linux 1.61%
Mac OS X 10.6 1.60%
Mac OS X 10.7 1.56%
Mac OS X 10.9 0.84%
Mac OS X 10.5 0.33%
Windows NT 0.08%
Mac OS X 10.4 0.08%
Windows 2000 0.03%
Mac OS X (no version reported) 0.01%
Windows 98 0.00%
FreeBSD 0.00%
SunOS 0.00%