Windows Executable Walkthrough Graphic
One of the things that's held back Windows and made it so complex, according to an MS engineer I recently spoke with who's been with the company since the 80's, is that it contains thousands of pieces of code to fix bugs in third-party software.In other words, there's code in Windows 7 that prevents crashing due to a rare bug in Where In The World Is Carmen Sandiego v1.3 (hypothetical  example). And so on.