Microsoft has released the first major update to its Windows Vista operating system on Tuesday, promising better performance and increased stability.

The Redmond, Wash.-based software company put the update onto its website, allowing consumers who already run the company's latest operating system to download a free upgrade.

Early testers of the update have widely reported that the service-pack will improve performance, most notably in file-copying and playing games originally designed for Windows XP, Microsoft's previous operating system.

Most software will continue to work as normal, the company said, however Microsoft did mention a list of applications it has blocked 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.

SP1 will also remove from Vista the so-called Kill Switch -- a feature that deactivated key components of the OS if Microsoft detected users were not running a properly licensed copy of Vista.

The feature was plagued by false alarms that flagged thousands of legitimate Vista users as software pirates.

Web retailer Amazon.com Inc. is selling boxed copies of Vista SP1 for shipping Wednesday.

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