Developers writing Vista-compatible applications will be unable to use Visual Studio 2002 or Visual Studio 2003 if those are running on top of the new operating system, wrote S. Somasegar, vice president of Microsoft's developer division, in a blog entry.

The requirement was included as part of announcement of Service Pack 1 (SP1) for Visual Studio 2005, which was released Tuesday on the Microsoft Connect Web site for developers.

Microsoft is making the move to accommodate major changes in the way Vista works, said Jay Roxe, group product manager for visual studio. New features such as Windows Presentation Foundation and Aero and Glass take such a vastly different approach from previous operating systems that they wouldn't be well served by older development programs.

"You need the new tools to take advantage of the new features," Roxe said in an interview. Developers may still write Vista software using older versions of Visual Studio as long as they are running on Windows XP, he said.

Somasegar's blog entry also told developers who run SP1 on Vista to expect "compatibility issues." Roxe said incompatibilities include the inability in most cases to register com components, requiring the use of a command line. To work around other problems, developers may need to run SP1 on Windows XP, he said.

Microsoft plans to offer a Visual Studio update fixing the shortcomings after Vista is released to consumers, Roxe said.