A Service Pack 1 near-final "release candidate" can now be downloaded, despite initially being restricted to 15,000 beta testers.
According to a blog by ZDNet.com's Mary Jo Foley, a Microsoft representative said the build contained a "number of bugs that testers encountered in previous prerelease versions of SP1."
The update is largely a collection of bug fixes and performance and compatibility improvements, but includes some minor new features.
SP1 RC Refresh, as the update is known, requires previous versions of SP1 to be uninstalled before it can be replaced with Refresh, which may entail waiting for the computer to "reboot multiple times," according to Microsoft.
After multiple rebooting, a period of an hour is required to allow the installer service to "clean up and complete the uninstall" to prevent possible installation errors.
Those with Vista RTM need to install two to three updates, depending on their version of Vista, before they can welcome SP1 onto their computer.
Refresh is time-limited, with the deadline for uninstall being June 30, 2008. According to Foley, Microsoft still aims to have the official version of SP1 available within the first quarter of 2008.
On its Web site, Microsoft warned that it "does not recommend installing this software on primary or mission-critical systems."
Suzanne Tindal of ZDNet Australia reported from Sydney.