Microsoft is set to release Windows Vista Service Pack 1 to consumers, according to information posted on Amazon.com and reports from a website that correctly called SP1's manufacturing ship date last month.

Amazon currently lists Vista SP1 retail copies as available from Wednesday 19 March, while Techarp, the Malaysian site that nailed the update's release to manufacturing (RTM) date several days early, said users would be able to download SP1 starting tomorrow.

Vista SP1 shipped to duplication and OEMs on 4 February, but since then it has only been available to previous beta testers, volume licensing customers and subscribers to IT subscription services. In fact, subscribers to TechNet and Microsoft Developer Network (MSDN) only got access to SP1 after raising a ruckus, with some threatening to cancel their subscriptions, and others saying they would postpone Vista deployment.

Most Vista users, however, have been unable to obtain the service pack. That was a conscious decision on the part of Microsoft, which said that the delay was caused by a small number of hardware device drivers that won't properly reinstall during the SP1 upgrade. Microsoft said it needed extra time to identify the drivers and set up blocking mechanisms that would prevent users whose PCs have those drivers from receiving SP1.

Microsoft has never identified the faulty drivers or the responsible hardware manufacturers.

When asked to confirm the 19 March delivery date, a Microsoft spokeswoman only repeated the company's earlier statements. "In mid-March, we will release Windows Vista SP1 to Windows Update and the download centre on Microsoft.com," she said. "Customers who visit Windows Update can choose to install Service Pack 1. Any system that Windows Update determines has a driver known to not upgrade successfully will not be offered SP1."

It's unclear so far how a February snafu will affect SP1's roll-out. Last month, after Microsoft pushed a pair of prerequisite patches to users, some reported that their machines refused to finish installing one of the fixes, then went into an endless series of reboots. Several days later, Microsoft pulled the update from automatic delivery, said it was working on a solution and promised it would "make the update available again shortly after we address the issue."

Microsoft has repeatedly insisted that the endless reboot problem and the subsequent withdrawal of that update (designated 937287) would not impact SP1's schedule.