Hi - there is a similar but not identical posting http://www.bleepingcomputer.com/forums/t/573663/changed-microsoft-password-now-i-cant-log-in-to-computer/ so if I should move this there I will be happy to. However, my issue is slightly different so I didn't want to muddy the waters over there.
I purchased a Lenovo desktop "certified" open box from BB but it was a hacked up sw mess. At the time it took days to get the Win8 updates (there are documented network driver issues from that time period). Finally got it updated then upgraded to 8.1. First mistake (well first after my purchasing decision! I didn't do my research and realize I could create a local acct as it only prompted to enter a MS Live account.
I was hit with problems that are documented by many users at that time - a) Win updates reset nw drivers, breaking connectivity, and requiring an edit of Win settings to use correct drivers; Win 8/8.1 loses or corrupts login passwords. When this occurred (after a forced Win update) I could not logon.
I contacted MS and was instructed to reset password. I confirmed the password reset by accessing my hotmail account on a different computer. However, the desktop in question never successfully updated the password, and after another reboot the network connectivity was lost (again). This time, however, I could not edit the settings to regain connectivity because I couldn't access Windows (due to the password issue).
I tried using the sticky key hack, using restore/boot disks from the desktop as well as from other computers, to no avail. I was able to eventually get into safe mode under troubleshooting but I cannot access the hidden admin account/password because I'm always asked for a password. I did have a non-admin local acct but that pw was also hosed. The error msg was misleading - it was similar to "system not available try again later" so I thought it was another connectivity issue - it was only after many tries that the 'incorrect pw' msg would sporatically show.
The desktop is being used as a door stop now, but am hoping since there are other similar threads, maybe there is hope? I can't use a Tornado to connect, nor can I put in on my home network to access, but I'd really like to get to the bottom of the problem. I'm not a fan of pw breaking sw but even tried several - but it seems most are for local accts, and none I tried even found the non-admin local acct pw.
Sorry for the long msg - TIA for any tips.