Uwe Stöhr wrote:
When you install LyX using this installer: http://wiki.lyx.org/Windows/LyXWinInstallerall LaTeX-packages needed by LyX are automatically installed. All you need to do, is to have an open internet connection before you start to install LyX.
The standard installer does the same thing. Try Tools > Reconfigure and MiKTeX should try to download it again.
Joost
