Windows Vista Service Pack 1 (SP1) release-to-manufacturing (RTM) is set to become available for download by Technet and Microsoft Developer Network (MSDN) subscribers today, after Microsoft changed the release date for the final version of the update.

IT professionals and developers who are part of TechNet and MSDN pay hundreds of pounds per year for the right to download and test software before it's offered to the general public.

On the TechNet Plus blog, where subscribers had previously denounced Microsoft's decision to delay the final code until early next month - and then in a change announced Monday to a vague "later this month" - one Microsoft blogger confirmed that SP1 would be available to TechNet subscribers on the same day as those who are part of MSDN. "It will become available for both programs at once," said Kathy Dixon of Microsoft. Dixon was responding to a user who noted the availability change for MSDN subscribers.

Windows Vista SP1 review

Although Microsoft did not specify the day, today is the most likely candidate; earlier this week, the company said it would let Volume Licensing customers download the bits on Friday.

On February 4, when the company said it had wrapped up the long-anticipated service pack and shipped it to OEMs for use in new PCs and to duplicators to begin the process of assembling retail packages, it noted that the most current Vista users would not get it until mid-March. Mike Nash, vice president of Windows product management, explained then that the company needed time to identify hardware device drivers that might give some users trouble during an upgrade.

While most subscribers leaving comments on the TechNet Plus blog acknowledged that it made sense to delay SP1's delivery via Windows Update, they questioned the rationale for not making it available to the technical crowd through a manual download from Microsoft's website. Some IT administrators, in fact, admitted that they had downloaded pirated copies to begin testing, while others claimed that the delay would jeopardise their Vista deployment plans or push them into dropping their TechNet subscriptions.

At times, the comments became heated. "Microsoft is currently the only place we can't download it from," said a user identified as 'IDontGetIt' last Saturday on the TechNet Plus blog. "And I feel lied to as well."

After the decision was announced on the MSDN Subscriptions blog on Thursday, users there were upbeat. "This is incredibly good news," said someone using the alias 'Kizzer'.

Vista SP1, which has been in testing since September, includes more than 550 security patches and bug fixes. It also includes a number of reliability and performance improvements and changes to features such as its desktop search and antipiracy technology.

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