Microsoft is confident it can deliver the first service pack (SP1) for its Vista operating system before the end of March, though the final release may slip back to the summer.

The final SP1 release will contain fixes and patches for bugs and security vulnerabilities discovered in the first year of the operating system's life, as well as updated device drivers and performance tweaks.

The first service pack is the trigger for widespread enterprise adoption of any operating system, because IT departments wait for the certainty that early bugs have been eradicated and the platform stabilised before migrating.

Microsoft released an early version of Vista SP1 to around 15,000 beta testers last week, but the code is not yet publicly available.

Service pack 3 for the earlier Windows XPoperating system is on track to be delivered in the first half of 2008, said Microsoft.