Every windows since Windows 95 have an NSA back-door put in. That is why the only secure way to use windows is on a virtual machine.
Proof, please? No? Didn't think so.
I highly doubt there's any obvious "back doors" anywhere in Windows. First, large portions of NT4 and somewhat smaller portions of Win2k have been leaked to the public. Universities and others have had access to much larger subsets under NDAs. People have been scrutinizing the binaries in search of 0-day exploits, to subvert kernel protection, the license codes, windows genuine advantage, et cetera. If there were deliberate backdoors, they would have been found.
That's not to say there might not be some buffer overflows or whatnot that have been put there for the purpose of creating a backdoor, though. But I kinda doubt it, it would be a lot safer to be able to truthfully & fully disclaim such allegations, and utilize one of the numerous accidental 0-day exploits.