Code:
public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private OleDbConnection CN = new OleDbConnection();
        private DataTable zaGrid;

        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();

            zaGrid = new DataTable();
            DataColumn colStatus = new DataColumn("zavrseno", typeof(bool));
            DataColumn colSubjekat = new DataColumn("tema", typeof(string));
            DataColumn colIme = new DataColumn("ime", typeof(string));
            DataColumn colImeOca = new DataColumn("ime_oca", typeof(string));
            DataColumn colPrezime = new DataColumn("prezime", typeof(string));
            DataColumn colRJ = new DataColumn("rj", typeof(string));
            DataColumn colDatum = new DataColumn("datum", typeof(string));
            DataColumn colVrijeme = new DataColumn("vrijeme", typeof(string));
            DataColumn colAlarm = new DataColumn("alarm", typeof(bool));
            DataColumn colID = new DataColumn("id", typeof(long));

            zaGrid.Columns.Add(colID);
            zaGrid.Columns.Add(colIme);
            zaGrid.Columns.Add(colImeOca);
            zaGrid.Columns.Add(colPrezime);
            zaGrid.Columns.Add(colRJ);
            zaGrid.Columns.Add(colDatum);
            zaGrid.Columns.Add(colVrijeme);
            zaGrid.Columns.Add(colSubjekat);
            zaGrid.Columns.Add(colAlarm);
            zaGrid.Columns.Add(colStatus);

            dataGridView1.DataSource = zaGrid;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OleDbDataAdapter adapter;
            adapter = new OleDbDataAdapter("select * from task",CN);
            adapter.Fill(zaGrid);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            OleDbDataAdapter adapter = new OleDbDataAdapter("select * from task", CN);
            OleDbCommandBuilder mySqlCommandBuilder = new OleDbCommandBuilder(adapter);
           
//ovdje mi izbaci gresku...
            adapter.Update(zaGrid);
        }
    }