Microsoft will make available to beta testers an updated release of its Windows Server 2003 Service Pack 1 (SP1), its new 64-bit edition of Windows XP and its 64-bit editions of Windows Server 2003 on Tuesday evening.

AT 6 p.m. PST, the company is set to post for download the new "Release Candidate 2" (RC2) beta builds of SP1 and its x64 editions, company officials confirmed. SP1 is the underlying technology upon which the x64 releases and Windows Server 2003 R2 build. It will consist primarily of security fixes akin to those Microsoft delivered with Windows XP Service Pack 2, plus a new Security Configuration Wizard.

The final versions of SP1 and the x64 Windows client and server editions are due in the first half of 2005. Some industry watchers have pegged April as the likely final delivery date, since that is when Microsoft will be holding its annual Windows Hardware Engineering (WinHEC) conference.

Microsoft officials said there are no major feature changes between the Release Candidate 1 builds of SP1 and the x64 Server editions, which Microsoft made available in December 2004, and RC2.

"The difference between RC1 and RC2 really is one of increased robustness as Microsoft prepares for the final RTM," or release to manufacturing, a company spokeswoman said.

However, "one notable change for RC2 for SP1 is that Microsoft added a link to the desktop pointing users to the Security Configuration Wizard. This change was made based on feedback that the link was difficult to find in RC1," the spokeswoman added.

Microsoft is making the RC2 releases available to members of the Microsoft technical beta program. The company also is making the code for Windows XP Professional X64 edition available to some customer testers, via the company's Customer Preview Program.

Windows Server 2003 x64 Editions and Windows XP Professional x64 Edition are both designed to allow customers to run both 32-bit and 64-bit applications.

Microsoft also will announce later this evening that it will begin accepting hardware device submissions for both Windows XP Professional x64 Edition and Windows Server 2003 x64 Editions for the "Designed for Windows" logo program in the coming weeks, the spokeswoman said.