Hi. I also cannot seem to disable my password upon opening my laptop. I scanned as best I could through this thread, but may have missed this if it has already been mentioned. I feel it's worth bringing up in case no one else has noticed this same problem. I followed all the netplwiz instructions many times as well and then I realized that when it brings me up to the popup asking for my password......the "username" is not correct. I hadn't really paid attention because the cursor goes right to the password field so I guess I just presumed the preprinted username was right.
So, for example if my username was (e-mail address removed) it is only showing abcde and it completely removes the rest of my email address. I correct it, and yet it keeps reverting back to the wrong username, and thus continues to ask for my password upon opening my laptop. Very frustrating.