If you are looking for the leaked MS source code, don’t do it. As John Lettice points out:
…if you are offered unlicensed access you're smart not to even look at it, because simply knowing how the stuff works compromises your ability to produce products independently, and renders you difficult/dangerous to employ in the relevant field.
And later …
Finally, this is very important: if you propose to continue working in the IT industry, and somebody offers you a look at the source, just say no. Remember - if you learn too much about the internals of Microsoft products, you may find yourself unable to work for anybody except Microsoft. Yikes.
This statement is obviously fact. Don Box told us all about COM internals, and guess where he works now? Microsoft. Chris Sells has openly admitted to pumping MS employees for insider information at trade shows. Guess where Chris works now? Microsoft.