From Microsoft:

The Microsoft Visual C++ 2005 Redistributable Package (x86) installs runtime components of Visual C++ Libraries required to run applications developed with Visual C++ on a computer that does not have Visual C++ 2005 installed. This package installs runtime components of C Runtime (CRT), Standard C++, ATL, MFC, OpenMP and MSDIA libraries.

For libraries that support side-by-side deployment model (CRT, SCL, ATL, MFC, OpenMP) they are installed into the native assembly cache, also called WinSxS folder, on versions of Windows operating system that support side-by-side assemblies. This version is the first release on CNET Download.com.