After many rumors as to when Windows Vista would get its much-anticipated first service pack looked improbable, Microsoft has finally dropped SP1 on the masses. SP1 rolls together 23 security updates and 550 hotfixes into a 434.5MB download (726.5MB for the 64-bit version). Apart from improvements brought by individual updates that are now part of SP1, changes that SP1 brings by itself to Microsoft's flagship OS are numerous. Significant changes include:

File copying should no longer have an ETA of hundreds of years

UAC has been altered slightly, including fewer prompts in specific scenarios

DirectX has been updated to support not only DirectX 9 and 10 hardware, but the backwards-compatible 10.1 as well

WGA has been tweaked to address two of the most popular exploits

Further support has been added for third party search solutions

Currently, the service pack is only available to users running English, French, German, Japanese and Spanish versions of Windows Vista, or Ultimate users that have only these language packs installed. Both x86 and x64 flavors are available via Windows Update (~65 MB) or from the Microsoft Download Center (434 MB). If they haven't already, Vista users need to first install three prerequisite updates before installing SP1, which makes Microsoft's latest client OS more aligned with its server offering.

Those who haven't yet moved to Vista can skip the whole updating process with the purchase of a retail copy of Vista plus SP1. The many editions of Vista are already available with SP1, and with a lower price tag to boot. Although at press time they weren't yet showing signs of change, OEMs are (hopefully) not far behind with systems that have Vista SP1 installed.

The other 31 language versions (both the actual service pack and the language packs for Ultimate users) are on their way, with an early-April date being bandied about for the full SP1 language spectrum. Furthermore, all language versions of SP1 will reportedly be pushed automatically through Windows Update on or after April 18, for those that have set the built-in Windows Update client in Vista to automatically download and install updates.

Vista SP1 hit the Release to Manufacturing (RTM) milestone in early February, but the good news was quickly buried. Microsoft disclosed an unexpected delay, saying that the company needed to work with certain hardware manufacturers to bring their problematic device drivers up to speed. Microsoft has said that SP1 will not become available for PCs with hardware or peripherals that have these drivers until they are updated.

Many tech-savvy users were not happy with the news of having to wait for Vista SP1 RTM (which is actually SP1 RC Refresh 2 in disguise). Microsoft listened to their complaints, and changed its mind: the company gave SP1 to its beta testers, volume licensing customers, and MSDN and Technet Plus subscribers. In addition to these users, SP1 x64 was released accidentally on Windows Update to lucky individuals on February 21.

As with any update as major as SP1, problems are to be expected. Even before it was released, Microsoft had to pull a prerequisite update due to an infinite reboot loop a handful of users were seeing. Unfortunately, this is only the beginning of problems that small groups of users will probably experience.

Cries of the issues that select few have with the service pack installation will most likely drown out talks of the many setup and deployment, application compatibility, performance, power consumption, security, reliability, and interoperability improvements of the service pack that the majority are enjoying. As always, we recommend a clean install of the operating system, but regardless of which method you choose to install SP1 with, please don't forget to make a backup.

There's a lot riding on the release; Microsoft is quite aware of the rule of thumb many businesses have for a new OS release: don't deploy until the first service pack is available. Sure, there are more than 100 million Vista users out there at the moment, but everyone knows that once businesses begin switching en masse, the predecessor (in this case, XP) truly begins to fall.

SP1 needs to have as little problems as possible if businesses previously on the fence about Vista are to give the new operating system a second look. More virtual roundtables and tutorials for Vista deployment are most likely on their way in the coming weeks. Even if the update won't be bringing any revolutionary features, the thousands of tweaks and bugfixes are exactly what businesses care most about.

If you or your company hasn't moved to Vista yet, will SP1 make you take the plunge?

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