The leaked Windows XP code is well on the way to being a complete leak. There are a lot of missing parts in the code that was shared by someone called NTDEV, but there is a community working towards completing the code and getting a reliable build of Windows XP. This leak could have exposed a LOT of vulnerabilities in Windows XP, but there should be no one using it these days anyway. Any code in Windows 8.1 and 10 would be different by now. This seems like a strange project to take on, building ancient code, but there is also a project that is building the old Apollo code that ran on the computers in the Apollo spacecraft and they are getting the code to run and rebuilding the old spacecraft computers. I guess keeping history alive is a very good thing. Microsoft may not be happy with this project, but some people are very interested in how the Windows operating system works and are willing to invest the time to work it out. That is a fine use of your time I guess. Restoring Apollo guidance computers is a valuable recreation of history, compiling stolen Windows code is not.
But those who are invested in that project see it as a valuable investment of time and who am I to argue against it, even if I do not agree with the use and distribution of code that was leaked on to the Internet. But even if they get a working version of Windows XP to build reliably, what are they going to do with it? That is the real question.