The C:\Windows\WinSxS directory
The directory C:\Windows\WinSxS is the Side-by-Side store (also known as the "Windows component store"). It is conceptually the native equivalent of the .NET "Global Assembly Cache" (GAC). This directory contains the dll files and manifests associated with each Side-by-Side assembly. The size of this directory can grow to several GB in size as more applications are installed. As one might imagine however, uninstalling an application does not usually remove files from this directory, as the files could be needed by other applications. Note: Never modify the files in this directory.