WinDbg is a graphical debugger from Microsoft. It is actually just one component of the Debugging Tools for Windows package, which also includes the KD, CDB, and NTSD debuggers. Its claim to fame is debugging memory dumps produced after a crash. It can even debug in kernel mode. For downloads and more information.
Windows (x86) :: dbg_x86_126.96.36.1993
Windows (x64) :: WinDbg_x64
Official Website :: https://www.microsoft.com/