Today's applications span a wide variety of architectures and infrastructure configurations including complex multi-tier configurations. Development and testing these applications require complex environments consisting of multiple physical systems and network connections. These requirements result in significant costs and configuration effort.

For example:

Applications overwrite common settings in the Windows® Registry, install different versions of components, and utilize common resources, de-stabilizing the functionality of other installed applications.
Different versions of the same application often cannot run simultaneously on a single computer. One version may overwrite the settings or contents of the other.

Because you never know which applications will conflict, IT must spend hours, days and even weeks regression testing them on staging machines and then on production systems, before deployment.