The first Service Pack for Windows Vista is made available as the latest Windows client has firmly established itself as the runner-up of Windows XP. Vista passed the 100 million install base milestone by the end of 2007 and managed to grab a share of between 13.24% and 14.02% of the operating system market, at the direct expense of its predecessor. Judging by the correlation between market share and the number of sold licenses as reported by Microsoft, in the first three months of 2008, Vista, even without SP1 sold in approximately 30 to 40 million copies.

Internet metrics company OneStat puts Vista's global usage share at 13.24%. "Microsoft's Windows dominates the operating system market with a global usage share of 95.94%. In July 2007 the total global usage share of Microsoft's Windows was 96.72%. A remarkable fact is that since July 2007 Microsoft's Windows Vista has gained 10.01% in global usage, and Windows XP has dropped 8.43%. The leading operating system on the web still remains Microsoft's Windows XP with a global usage share of 78.93%. The global usage share of Apple's Macintosh is 3.36% and the global usage share of Linux is 0.42%," OneStat revealed.

In terms of Windows Vista's market share, the data provided by OneStat coincides with the statistics made available by Net Applications. According to Net Applications, Vista has climbed all the way to 14.02%. But outside of coming to approximately the same conclusion for Vista, the rest of the data from Net Applications diverges from OneStat's perspective. Net Applications puts Windows XP at 73.59%, MacIntel at 4.54%, Mac OS at 2.94% and Linux at 0.61%. It is the general tendency of the introduction of SP1 to accelerate the adoption of the respective Windows client, but only time will tell if Vista SP1 will outperform Vista RTM in terms of uptake. Vista SP1 was released to manufacturing on February 4, 2008, and to the general public on March 18.