To change the SQL sa password from a command prompt:

Start a command prompt by typing StartRuncmd

Table of Contents

    Enter the following commands, pressing Enter after each line

    OSQL -S yourservername -E
         1> EXEC sp_password NULL, 'yourpassword', 'sa'
         2> GO

    Where yourservername is the name of your server and yourpassword is the new sa account password.  Type exit twice to return to the server desktop.

    This works in SQL 2005, I don’t have access to other versions so I can’t say if it will or won’t work other versions of SQL.