WSJ had an interview with Jim Allchin, a senior Microsoft executive, about Windows Vista. He says in July 2004 he walked into Bill Gates's office to tell Longhorn isn't going to work. He claimed the next-generation if Windows was so complex that its writer would never be able to make it run properly..
Mr. Allchin says he soon saw his fears realized. In making large software programs engineers regularly bring together all the new unfinished features into a single "build," a sort of prototype used to test how the features work together. Ideally, engineers make a fresh build every night, fix any bugs and go back to refining their features the next day. But with 4,000 engineers writing code each day, testing the build became a Sisyphean task. When a bug popped up, trouble-shooters would often have to manually search through thousands of lines of code to find the problem.
Mr. Gates's WinFS project was so troublesome that engineers began talking about whether they could make the "pig fly." Images of pigs with wings started appearing in presentations and offices.