Despite being released to manufacturing last week, Windows Vista Service Pack 1 is not being made available to all customers because Microsoft is trying to resolve an issue in which hardware devices may stop functioning after SP1 is installed.

Apparently, there is a problem that can occur when the operating system re-installs drivers after SP1 is loaded onto a system. Microsoft says the drivers themselves are not at fault, but ostensibly because Vista SP1 is already finalized, the company has opted to work with hardware manufacturers to implement fixes.

According to Microsoft, the problem affects only a "small set" of hardware device drivers, but that could still involve millions of customers.

Nash said Microsoft actually knew of the issue before releasing the final version of Vista SP1, and that beta testers were able to work around it by uninstalling and reinstalling the drivers on their own. Microsoft doesn't expect normal consumers to do this, of course, which is why it's working with manufacturers on changing the drivers instead.

It's not clear why Microsoft didn't give driver manufacturers advance notice of the required changes, nor why the problem wasn't simply fixed in the service pack.

Regardless of the issue, beta testers for SP1 were given access to the RTM code late Friday. At the end of this week, Microsoft's Volume Licensing Customers will receive SP1. MSDN and TechNet Plus subscribers will be able to download the update by the end of the month, Microsoft says.

So when will you be able to download Windows Vista SP1? Microsoft has currently scheduled a public release for mid-March. This will give the company time to work through the driver issue without updating the SP1 code.

"We do not plan to make any changes to the SP1 code prior to public availability," concluded Nash. "We are confident in the quality of Windows Vista SP1 and know that it will help improve our customers' experiences with Windows Vista."