Quick Answer: Side-by-side assembly technology is a standard for executable files in Windows 98 Second Edition, Windows 2000, and later versions of Windows that attempts to alleviate problems that arise from the use of dynamic-link libraries in Microsoft Windows. Such problems include version conflicts, missing DLLs, duplicate DLLs, and incorrect or missing registration. In side-by-side, Windows stores multiple versions of a DLL in the %systemroot%\WinSxS directory, and loads them on demand. This reduces dependency problems for applications that include a side-by-side manifest. Microsoft Visual C++ 2005 and 2008 employ SxS with all C runtime libraries. However, runtime libraries in Visual C++ 2010 no longer use this technology; instead, they include the version number of a DLL in its file name, which means that different versions of one DLL will technically be completely different DLLs now. SxS is also the technological basis for registration-free COM activation.