support.microsoft.com/en-us/kb/2795190

When you examine the size of the C:\Windows folder, you may notice that the C:\Windows\winsxs directory seems to use lots of disk space.

blogs.technet.com/b/askcore/archive/2008/09/17/what-is-the-w...

A commonly asked question among people looking at a Windows Vista or Windows Server 2008 installation is “why is the WinSxS folder so big?!” To answer that question I need to first describe componentization, and how components are managed i ...

helpdeskgeek.com/windows-8/cleanup-the-winsxs-folder-in-wind...

In Windows 7 and Windows 8, there is a new folder under C:\Windows called WinSxS, which basically stores dll and component files. It also stores older versions of all dll and component files and can grow to be quite large. In addition to that, a lot of ...