in-place upgrade - Computer Definition
The installation of an operating system or application on the computer without removing the older version first and without saving any data beyond normal precautions. In-place installations of operating systems have a tendency to cause problems, especially if the new version is very different from the previous one. For example, in-place upgrades are recommended when migrating from Windows Vista to Windows 7, but not from Windows XP. In that case, a "clean install" is recommended, whereby all user data have to be saved externally and restored after the installation, and all applications have to be re-installed. Contrast with clean install.