Do anyone know where the password file is stored in pc(user account's) ?

Here is the answer for it

Yes password file was stored in windows system32 config and sam file

named as SAM

location : C:\windows\system32\config\SAM


we can change password by entering into the location given above.
limitation:
you cant access properly if you have not the administrator rights even you can do the changes if you are added in the power user list other wise you cant do anything with the limited account.

But you can do using cmd as given below

Go to Dos type net user administrator *
press enter now type your own password
So now you have hacked the administrator