"Once a server application is up and running, it's very unusual for it to be repurposed," says Jonathan Eunice, an analyst at Illuminata Inc. "It's almost never done, and that's true of Windows to Linux and Linux to Windows."

The rare cases in which companies did migrate a Windows-based system to Linux, or vice versa, illustrate why such moves aren't going to turn into a hot trend anytime soon. The problem isn't just the hard work and the differing skills and development tools that are needed. The old adage, "if it ain't broke, don't fix it," tends to rule.

A Case in Point

State Street Corp. undertook a Windows-to-Linux project when it wanted to beef up the functionality of an internally developed fund administration application. The Boston-based financial institution also wanted to enable more employees to use the application, which collects data from a variety of sources, to prepare reports for outside customers. To add the new capabilities, the IT department determined that it would need to change the front-end user interfaces and redesign the database for the Windows-based application, which used Microsoft's Access and SQL Server databases.

State Street tends to view its IT landscape from the standpoint of scale. Mainframes, Unix and Linux are favored when the company plans to run the application at an enterprise or global level. Windows is typically the choice for smaller applications, when integration with the desktop environment is an important criterion or when the company won't have the resources to provide local support, says David Saul, a senior vice president in the office of IT architecture at State Street.