Editing Service pack (section)

==Impact on installation of additional software components==
Application service packs replace existing files with updated versions that typically fix bugs or close [[Vulnerability (computing)|security hole]]s. If, at a later time, additional components are added to the software using the original media, there is a risk of accidentally mixing older and updated components. Depending on the [[operating system]] and [[Software deployment|deployment]] methods, it may then be necessary to manually reinstall the service pack after each such change to the software. This was, for example, necessary for [[Windows NT]] service packs; however, from [[Windows 2000]] onwards, Microsoft redirected setup programs to use updated service pack files instead of files from the original installation media in order to prevent manual reinstall.<ref>[http://support.microsoft.com/kb/274215 Not Necessary to Reinstall Windows 2000 Service Packs After System State Changes]</ref>