Mudar o SQLEXPRESS para mixed Mode:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.1\MSSQLServer

LoginMode =2

Criar usuário no SQLEXPRESS

SQLCMD -S.\SQLEXPRESS -E

sp_addLogin ‘username’, ‘pass’
GO
sp_addsrvrolemember ‘username’, ‘sysadmin’
GO