Thanks to Denis Ducamp for changing chntpw to use OpenSSL.
Explanation of win3.11, win95 and most important NT registry files can be found in WinReg.txt, written by some German (I think, at least speaks German) named B.D. Sorry I don't have that persons full name, I can't find a name/address in the file, and it was not credited when I picked it up from some website. This is the original file as I found it, I've discovered some minor errors, but not corrected the file. Look it up in my sourcecode for more detailed info.
For more info on the SAM part of the registry, look at the NTBugTraq Article List, it contains some FAQs etc about password storage in NT.