To change SQL password is easy .Just follow steps given below :
change sql server password
Changing SQL Server user password by using MSSQL Server Management Studio Express .
Just Login to your Server using MSSQL Server Management Studio Express . Make sure to specify the correct SQL server for your database .
Expand the tree menu on the right by clicking on the "+" next to Security followed by clicking on the "+" next to Logins . Your users for the database in question should be listed .
Right click on the user you wish to change the password for and choose the Properties option at the very bottom of the menu .
Under the general section of the window you will see the option to type in and confirm a new password . Once the new password has been typed in , then click the "Ok" button in the lower right to finish .
That's it .