Microsoft on Tuesday made available to beta testers a nearly finalized version of Windows Server 2003 Service Pack 1.

The vendor also made available the so-called "release candidates," software for which beta testing is nearly complete, for Windows Server 2003 x64 Editions and Windows XP Professional x64 Edition. Both those platforms are slated for final release in the first half of 2005.

Windows Server 2003 Service Pack 1 was originally scheduled to ship by the end of the year, but in October Microsoft pushed the release date into the first half of 2005. Service Pack 1 includes all the updates released since Windows Server 2003 shipped plus upgrades that align the server software with security components released in the desktop operating system Windows XP, most notably the Windows Firewall.

Microsoft also is including quarantine technology that is the first phase of Network Access Protection (NAP), a set of technologies built into Longhorn for evaluating desktop computers for security compliance before letting them on a network.

Service Pack 1 will become the foundation for Windows Server Update, code-named R2, which will ship in the second half of 2005. R2 will include new storage management capabilities and such features such as branch server management and Active Directory Federation Services. Microsoft plans to release R2 at no charge for Software Assurance customers, but will require purchase of a new server license for those not on the software maintenance plan.

Also on tap is an R2 version of Windows Storage Server, a specially tuned OS made available to OEMs.

With its new 64-bit versions, Windows Server 2003 x64 Editions and Windows XP Professional x64 Edition, Microsoft is providing users with the option of running both 32-bit and 64-bit applications on the same platform.

"It looks like the overhead of running 32-bit applications on x64 systems will be low," says Al Gillen, an analyst with IDC who recently reviewed the platform. "What that means is that it is going to make it so that there is almost no impediment to going to a 64-bit system."

But Gillen said he still thinks uptake will be slow because users will look at the x64 platform as a new OS. "I think people will stay on the 32-bit platform until they have demands for a 64-bit platform."

Windows Server 2003 x64 Editions and Windows XP Professional x64 Edition release candidate code is available for members of the Microsoft technical beta program. In 30 days, it will be made more widely available via the Customer Preview Program.

The release candidate of Windows Server 2003 Service Pack 1 is available online.