Microsoft Windows Vista SP1 is available through Windows Update service and retailers. The Service Pack 1 is free to download beginning Tuesday.
Online retailer Amazon is also taking pre-orders for boxed copies of Windows Vista Service Pack 1, which it said it will start shipping Wednesday.
The software giant previously announced plans to post SP1 to its Windows Update site and to its download center in mid-March, then push out the upgrades in mid-April to computer users who have set their PCs to receive automatic updates.
Vista SP1 improves Vista’s reliability, security and performance. Some early testers of the service pack have noticed improvement in performance when copying files over a network and playing video games that weren’t designed for Vista.
Microsoft said it has determined that only a handful of Windows programs will break down in some way after SP1 is installed.
SP1 will also block several applications from running for “reliability reasons.” The list includes BitDefender Antivirus and Internet Security, version 10; Fujitsu’s Shock Sensor hard drive protection for rugged laptops; two versions of Jiangmin KV Antivirus software and Check Point Technologies’ Zone Alarm Security Suite.