Microsoft has further delayed versions of Windows with 64-bit extensions until next year.

Windows XP 64-bit Edition for 64-bit Extended Systems and Windows Server 2003 for 64-bit Extended Systems now will not be available until the first half of 2005, a Microsoft spokeswoman announced.

The 64-bit Windows XP client was originally due in early 2004 but had already been delayed; the server software was scheduled for late 2004.

Microsoft is pushing back the two versions of Windows with 64-bit support and the service pack because it wants to thoroughly test the software with Windows XP Service Pack 2 (SP2), a significant update to Windows XP that is due in August, the spokeswoman said.

The new Windows editions are designed to take advantage of 64-bit extensions to the standard x86 instruction set in processors from both AMD and Intel. 64-bit systems offer users greater computing power as systems can process more data per clock cycle and have greater access to memory.

One key benefit of 64-bit extension technology is that applications written for 32-bit computers will run well on the processors. The 64-bit extensions are currently supported in AMD's Athlon64 and Opteron processors, as well as Intel's Xeon processor, code-named Nocona, released late last month.

Microsoft has high expectations of 64-bit technology. In May Bill Gates predicted that by the end of 2005 all the processors sold by AMD and the majority of processors sold by Intel will support 64-bit computing.

However, by pushing back 64-bit Windows, Microsoft is slowing down the trend of a desktop move to 64-bit, said Michael Cherry, a lead analyst at Directions on Microsoft, a research company.

"There are a lot of people who would be considering 64-bit, but I think this delays the customer interest in 64-bit for Windows systems. I would be reluctant to buy a 64-bit processor now if there wasn't much that I could run on it," Cherry said.

Also, Microsoft's call out to hardware makers to develop drivers for the new 64-bit editions of Windows may find less response now, Cherry said. "People may say, 'Gee, why should I work on the drivers if Microsoft is not working on the software'," he said.

"I would not say anything dramatic as that this opens a huge strategic hole for Microsoft, but at some point this hurts Microsoft's position against Linux, against all the 64-bit platforms already out there," said Gordon Haff, a senior analyst at Illuminata.

Microsoft offers test versions of the 64-bit Extended Systems editions of both Windows Server 2003 and Windows XP.

The software currently works only with AMD processors, but future beta versions will be released that support both AMD Opteron and Intel Xeon with Intel Extended Memory 64 Technology (EM64T), according to Microsoft.