Code:
private DataTable dTable;

        public Form1()
        {
            InitializeComponent();
        }
        private OleDbConnection CN = new OleDbConnection();

        private void Form1_Load(object sender, EventArgs e)
        {
            string sProvider = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\\projects\\c#\\Registar\\Registar\\bin\\Debug\\Data\\data.mdb;Persist Security Info=False;Jet OLEDB:Database Password=";
            CN.ConnectionString = sProvider;
            CN.Open();

            dTable = new DataTable();
            DataColumn colZavrseno = new DataColumn("status", typeof(bool));
            DataColumn colZadatak = new DataColumn("zadatak", typeof(string));
            DataColumn colPrezime = new DataColumn("prezime", typeof(string));
            DataColumn colIme = new DataColumn("ime", typeof(string));
            DataColumn colRJ = new DataColumn("rj", typeof(string));
            DataColumn colDatum = new DataColumn("datum", typeof(string));
            DataColumn colIzvrsenje = new DataColumn("izvrsenje", typeof(string));
            DataColumn colKR = new DataColumn("kljucna_rijec", typeof(string));
            dTable.Columns.Add(colZavrseno);
            dTable.Columns.Add(colZadatak);
            dTable.Columns.Add(colPrezime);
            dTable.Columns.Add(colIme);
            dTable.Columns.Add(colRJ);
            dTable.Columns.Add(colDatum);
            dTable.Columns.Add(colIzvrsenje);
            dTable.Columns.Add(colKR);

            dataGridView1.DataSource = dTable;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OleDbCommand selectCommand = new OleDbCommand("select status,zadatak,prezime,ime,rj,datum,izvrsenje,kljucna_rijec from zadatak",CN);

            OleDbDataReader dReader = null;

            dReader = selectCommand.ExecuteReader();

            if (dReader.HasRows)
            {
                while (dReader.Read())
                {
                    dTable.Rows.Add(dReader["status"], dReader["zadatak"], dReader["prezime"], dReader["ime"], dReader["rj"], dReader["datum"], dReader["izvrsenje"], dReader["kljucna_rijec"]);
                }
            }
            dReader.Close();

        }

        private void button2_Click(object sender, EventArgs e)
        {
            OleDbDataAdapter adapter = new OleDbDataAdapter("select * from zadatak", CN);
            OleDbCommandBuilder mySqlCommandBuilder = new OleDbCommandBuilder(adapter);
           
            adapter.Update(dTable);
        }

Code:
DataRow row;
row = dTable.NewRow();
row["status"] = false;
row["zadatak"] = "zadatak";
row["prezime"] = "prezime";
row["ime"] = "ime";
row["rj"] = "rj";
row["datum"] = "10.01.2007";
row["izvrsenje"] = "izvrsenje";
row["kljucna_rijec"] = "kljucna rijec";
dTable.Rows.Add(row);