Microsoft's slow march to service pack 3 for Windows XP continued Tuesday as the company released a refresh of its latest beta code.

The new software follows February’s release of Windows XP SP3 RC2. The newest beta release, however, only adds the word “refresh” to the title instead of updating the RC version.

“RC” stands for release candidate, which is a final beta before the code is considered finished.

The refresh designation was given to the code because Microsoft is using it to validate improvements to Windows Update for delivering XP SP3, Chris Keroack of the Windows Serviceability Team wrote in a posting on Microsoft TechNet.

The refresh code also includes support for HD Audio, but other than that contains no substantial changes from the XP SP3 RC2 (build 3311) code shipped last month.

The February release of the software included new networking, security and set-up functionality.

The service pack is only available via Windows Update in English, German and Japanese.

To get the code, however, users will have to run a script available from Microsoft that sets a registry key that allows Windows Update to recognize the PC as a target for XP SP3 RC Refresh. Users will need to uninstall XP SP3 RC1 and RC2 before running the script.

XP SP3 includes all the previously released updates for Windows XP, including security updates, and is for X86 machines only.

Windows XP was given a reprieve late last year when Microsoft extended its availability date to June 30, 2008. The software, which was the XP SP2 version that included security improvements, was originally slated to be taken out of OEM and retail channels on Jan. 30, 2008.

Microsoft extended the deadline after customers complained that they were not willing or ready to migrate to Vista.

Microsoft officials reiterated that the final version of XP SP3 would ship in the first half of 2008.

In its final release, XP SP3 will be supported as a guest operating system on Microsoft’s Hyper-V virtualization technology, which is slated to ship in the fall.

Microsoft last week released the first feature-complete beta of Hyper-V, which is an add-on to Windows Server 2008.