Hello.

I worked with a customer recently that reset the password to an account used for the farm admin account among other things in a development SharePoint environment.  Although there are a plethora of PowerShell commands this particular fix still requires stsadm.exe.  I found a nice article on TechNet for the procedure.  One thing to note if you have a SharePoint farm with > 1 SharePoint servers is that this command must be run on the server hosting the central administration website, otherwise it will fail.  The Technet Procedure is below, as well as a link to the webpage.

Change the passwords for the Central Administration Web application pool identity and the Windows SharePoint Services Timer service by using the command line

  1. On the computer running the Central Administration Web site, open the command line and navigate to the Program FilesCommon FilesMicrosoft Sharedweb server extensions12BIN folder.

  2. At a command prompt, type the following command, and then press ENTER:

    stsadm -o updatefarmcredentials -userlogin <domainusername> -password <newpassword>

    NoteNote: userlogin is the server farm account.
    For additional information, see Updatefarmcredentials: Stsadm operation (Office SharePoint Server).

  3. You must restart the Web application pool for the changes to be saved. At a command prompt, type the following command, and then press ENTER:

    iisreset /noforce

  4. On every other server in the farm, navigate to the Program FilesCommon FilesMicrosoft Sharedweb server extensions12BIN folder.

  5. At a command prompt, type the following command, and then press ENTER:

    stsadm -o updatefarmcredentials -userlogin <domainusername> -password <newpassword> –local

TechNet link: https://technet.microsoft.com/en-us/library/cc263417(v=office.12).aspx

-Dan