It's called the Vista Service Pack 1 Release Candidate Refresh. It's supposed to be a bug-fixin', feature-enhancin' behemoth that makes Windows Vista leaner, meaner, taller, and sexier.
It'll do your dishes and take out your garbage, too.
Microsoft released this "Release Candidate Refresh" late last week--just one month after the initial release candidate made its debut. The company asserted that it wants additional information from testers, which indicates that even more bugs need to be fixed. But what does RC Refresh really do? Is it really that large? Most importantly, do you need it?
Before we get to the nitty-gritty of whether it's worth downloading, the download itself needs a little explanation. First off, Microsoft warns that the SP1 RC and the Refresh should not be installed on primary or mission critical machines. Make of that what you will. Check out the changelog to Vista SP1 RC. If it's something you think your Vista installation needs, carry on. But keep in mind that, as a release candidate, it's not intended to be a fully stable version.
So, if you installed the original SP1 RC from December, you'll need to uninstall it. Go to your Control Panel/Windows Update/View Installed Updates, and then follow the instructions for uninstalling.
The official Microsoft instructions warn users to wait an hour after uninstalling Vista SP1 RC before installing the Refresh because "the installer service needs to clean up and complete the uninstall prior to installing the RC. Failing to do this can result in installation errors when installing the RC version."
Also note that you will be required to uninstall the SP1 RC Refresh before installing the full SP1 when it comes out. That's a lot of installing, uninstalling, and installing to do.
Just like when you were a kid and you had to wait after eating before you could jump back in the pool, you're going to have to get a book or take up knitting before downloading the installer. Once downloaded, extract the files and right-click on the CMD file. Choose Run as administrator. This creates a Registry key to allow the update to install.
Now go back to the Control Panel and go to System and Maintenance/Windows Update, turn automatic updating on, and select Check for updates. This way you stand a better chance of Vista detecting the SP1 RC Refresh on Microsoft's servers. Microsoft's documentation on the installation warns that it can take up to an hour to detect the patch.
The Windows Vista machine I use here runs Vista Enterprise. Vista's many strains includes some versions resistant to certain bugs, and other strains more susceptible. But all versions of Vista will work with the SP1 RC Refresh, which will autoinstall two patches before the full package is installed. However, as with the SP1 RC, the Enterprise and Ultimate versions will install an extra patch to make their BitLocker Encryption functions compatible.
Downloading and installing the patches takes a couple of hours, depending on how many updates your machine needs. However, more than 30 hours after first installing a clean version of the SP1 RC Refresh, it's still finding missing updates linked to the SP1. While the changelog for the initial Release Candidate was long and detailed, the new RC Refresh is beset by a dearth of information.
Given that, the amount of time it will take to load all the patches and bug fixes, and that some of those may not yet be ready for prime time, I'm going to recommend that most users give SP1 RC Refresh a pass until a better update comes out.
Only if you feel incredibly comfortable crippling your machine should you bother with this monstrosity.