Enable sa useraccountreset the password
osql -S YOURCOMPUTERNAME\SQLEXPRESS -E
1> alter login sa enable2> go
osql -S YOURCOMPUTERNAME\SQLEXPRESS -Eosql -S YOURCOMPUTERNAME\SQLEXPRESS -Eosql -S YOURCOMPUTERNAME\SQLEXPRESS -Eosql -S YOURCOMPUTERNAME\SQLEXPRESS -E