First, login to your Windows using an account in the admin group account ( note that only the admin group account has changed the admin password )
+ Then go to Run -> cmd press Enter, a Dos screen will appear
+ You type in the command " net user " and you will see a table of running accounts on your computer
+ Next, you type " net user nowares * ", a command line will appear showing how to change the pass account, domain .
+ You just need to follow, eg: I want to change admin pass, type net user Administrator {pass} , when the word successfully shows up is successful.
You can also go to google search to learn more about Dos commands.