Windows 10 - Disable Password Expiration

In an elevated Command Prompt
type:
wmic path Win32_UserAccount set PasswordExpires=False



Also, consider using Local Security Policy and Set Max Password Age to 0

Need to Reset Lost Windows 7 Password?

Either boot a Linux cd or
use the Windows 7 OS Disk
  choose REPAIR YOUR COMPUTER
  then Command Prompt

You can chosoe between using W\S32\sethc.exe or utilman.exe
Copy the original file for saftey
then copy cmd.exe over the selected file /y

When you restart and get tot he login screen
sethc - must hit shift 5 times in a row
utilman - click the icon in lower left

then use the following command:
  net user myusername mypassword
 and Login

When done, reverse the steps to put the original files back in place.

Very long post on long process involving Acronis

Read when have half an hour.
Note, is oldish.
http://arstechnica.com/civis/viewtopic.php?f=23&t=83414