"sa" is the default user that has administrator rights on the instance of SQL Server that you are using. The password for "sa" has been defined when SQL Server was installed on your computer. Please ask your system administrator for that password if the installation has been done by your IT department.

In case you have administration rights on your database engine, you can
a) Reset the sa password manually using SQL procedures. Steps to be performed are detailed below.
b) Install a new instance in the SQL server using the SQLExpress installation file in the ADOxx download package and define the password by yourself. This is done in the definition of the Authentication mode, that should be set to "Mixed mode" and the password for the "sa" user has to be entered. After that, please re-install ADOxx and make sure to use this password.

RESET "sa" PASSWORD on ADOxx

1) Check your instance name
As a first step you need to check name of the database instance you wish to connect to. It is shown during installation when question about SA password. Alternative way to check it:
Control panel>Services (on XP available under Administrative Settings) and search for the entry beginning with SQL Server. Most probably it will be SQL Server (SQLEXPRESS) --> in this case instance name is SQLEXPRESS.

2) Start the command line
Go to Start menu and use "Run" (for XP) or "Search programs and files" (Vista and Win 7), type:
CMD
and hit ENTER

3) Connect to the database
Assuming your instance name is SQLEXPRESS type:
osql -E -S .\SQLEXPRESS
and hit ENTER

4) Reset the password and exit
Assuming your new password is "newpassword" (your policy settings may force you to have something more complex) type the following after the prompt ("1>" for the first line etc.) appears. Hit enter after typing each line.
EXEC sp_password @new='newpassword', @loginame = 'sa'
go
EXIT

Please note: this is "loginame", NOT "loginname".