Boot to WinPE disc
At the console window (the black window)
Control-C
Select [Y] to break out
copy /y d:\windows\system32\sethc.exe d:\keep.exe (where d: is the Windows partition/drive)
copy /y d:\windows\system32\cmd.exe d:\windows\system32\sethc.exe
exit (computer will restart)
You may need to take ownership or change file attributes using the attrib command:
d:\windows\system32\attrib.exe d:\windows\system32\sethc.exe -r -h
Boot into Windows normally
After you see the logon screen, press the SHIFT key five times (a black window should appear)
type: net user USERNAME PW (the account name and password to reset)
copy /y c:\keep.exe c:\windows\system32\sethc.exe
exit
log in normally with new password