Microsoft has further delayed releasing its versions of Windows for PCs and servers equipped with x86 processors with 64bit extensions.

According to analysts the extra delay will slow the advent of 64bit desktop computing and provide a head start for rival operating systems on servers.

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

The 64bit 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 64bit 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 due out in August according to the spokesperson.

The new Windows editions are designed to take advantage of 64bit extensions to the standard x86 instruction set in processors from both AMD and Intel.

64bit systems offer users greater computing power as systems can process more data per clock cycle and have greater access to memory.

A key benefit of 64bit extension technology is that applications written for 32bit computers will run well on the processors. On the desktop side, the 64bit extensions are currently only supported in AMD's Athlon64.

However, by pushing back 64bit Windows, Microsoft is slowing the trend of 64bits on the desktop, says Michael Cherry, a lead analyst at Directions on Microsoft, a research company.

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