Windows Vista Service Pack 2 is set to be released as a public beta version Thursday, Microsoft has confirmed. The program, which has been under limited testing since October, will become available on the Microsoft TechNet site. Here's what you need to know before making the upgrade.

Vista Service Pack 2 isn't for everyone.

SP2 beta is, as the name suggests, a product still under development. Microsoft is recommending only "technology enthusiasts, developers, and IT pros" willing to test the software take on the upgrade. General users are advised to wait until the final release, which is set for the first half of 2009. Some unofficial reports indicate it is being targeted for an April completion.

SP2 is a fairly significant upgrade.

Windows Vista SP2 includes numerous changes to the Vista operating system. Here are some of the highlights of what it'll do for you:

• Let you record data onto Blu-ray discs

• Add into your system Vista Feature Pack For Wireless, which provides support for the latest Bluetooth technology -- Bluetooth v2.1 -- as well as for the Windows Connect Now (WCN) Wi-Fi protocol

• Give you better Wi-Fi performance when you're exiting Vista's sleep mode

• Make your RSS feeds sidebar gadget work faster and better

• Give you the latest desktop search engine, Windows Search 4

• Cut down the resources it takes to run your various sidebar gadgets

It'll give your OS an overall tune-up, too.

Vista Service Pack 2 will also deliver some under-the-hood improvements, which will:

• Give your computer support for VIA Technologies' new 64-bit CPU

• Let your system support exFAT, which can handle larger files and can also use UTC timestamps so you can synchronize files across different time zones

• Boost your power management efficiency by as much as 10 percent

Additionally, a slew of system bugs will be corrected in the update, including some slow shutdown problems and other crash-causing issues.

You have to have SP1 installed before you begin.

Like most Microsoft Service Packs, SP2 won't work on your system if you haven't already installed SP1. If you're thinking about trying the SP2 upgrade, you'll have to hit SP1 first.

Things may not be totally smooth at first.

Microsoft has had some history with glitches seemingly caused by its Windows Service Pack updates. It sometimes takes several hotfixes for these kinks to be worked out. That's precisely why it's often best to wait for the full release, at the very least, before jumping on the upgrade.

This Service Pack does offer some improvements over past ones.

Microsoft did take some steps to make this Service Pack function a bit better than past upgrades. It is the first Windows Service Pack to work for both the client (Vista) and server (Windows 2008) editions of the operating system in a single update.

SP2 also includes what Microsoft is calling a "Service Pack Clean-up Tool." This will permanently delete old versions of files SP2 is updating, helping you reduce clutter and get rid of outdated system files that'd otherwise just take up space.