This training course is a combined and reformatted version of the two previous books Windows Debugging: Practical Foundations and x64 Windows Debugging: Practical Foundations. The new format makes it easy to switch between and compare x86 and x64 versions. The book also has a larger format similar to other training courses from Software Diagnostics Services, punctuation and code highlighting improvements, the output and screenshots from the latest WinDbg 10, and consistently uses WinDbg (X86) for 32-bit examples and WinDbg (X64) for 64-bit examples. The book contains two separate sets of chapters and corresponding illustrations. They are named Chapter x86.NN and Chapter x64.NN respectively. There is some repetition of content due to the shared nature of x64 and x86 platforms. Both sets of chapters can be read independently. We included x86 chapters because many Windows applications are still 32-bit and executed in 32-bit compatibility mode on x64 Windows systems. This introductory training course can complement the more advanced course Accelerated Disassembly, Reconstruction and Reversing (ISBN: 978-1908043672).