Hi Friends,
    I am making a C# application that will create reports in Excel
from a database. My report involves creating many worksheets. Is there
any limitation for maximum worksheets in a workbook. As per Microsoft
the number of worksheets is only limitted by memory.. For me if i
create more than 256 sheets i get the exception with the value
0x800A03EC.

I get the exception here...
           sheet1 = (Worksheet)book.Sheets.Add(_missing,
(object)sheet1, (object)(260), _missing);
if i keep the worksheets to be less than 256 i am able to create the
report...

Ive given the code for the reference...

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Microsoft.Office.Interop;
using Microsoft.Office.Interop.Excel;

namespace MaxSheetsExcel
{

   public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
       }
       private object _missing = System.Reflection.Missing.Value;
       private string _filename =
@"D:\VDC_emailExport\ExcelTemplate\MaxSheetsExcel.xls";
       private string _template =
@"D:\VDC_emailExport\ExcelTemplate\Template_Def.xls";
       private void button1_Click(object sender, EventArgs e)
       {
           //MessageBox.Show("Button Clicked!");
           // excel objects
           Microsoft.Office.Interop.Excel.Application ExcelApp = null;
           Workbook book = null;
           Worksheet sheet1 = null;
           Workbooks books = null;

           ExcelApp = new
Microsoft.Office.Interop.Excel.Application();
           books = ExcelApp.Workbooks;
           //Hesri - Instead of creating a workbook from scratch make
use of a template
           //to create the report
           book = ExcelApp.Workbooks.Open(_template, _missing,
_missing, _missing, _missing, _missing, _missing, _missing, _missing,
           _missing, _missing, _missing, _missing, _missing,
_missing);
           //book = books.Add((object)XlWBATemplate.xlWBATWorksheet);

           sheet1 = (Worksheet)book.Sheets[1];
           sheet1.Name = "Report_parameters";
           for (int i = book.Sheets.Count; i >= 2; i--)
           {
               sheet1 = (Worksheet)book.Sheets[i];
               sheet1.Delete();
           }
           sheet1 = (Worksheet)book.Sheets.Add(_missing,
(object)sheet1, (object)(260), _missing);

           book.SaveAs((object)_filename, _missing, _missing,
_missing, _missing, (object)false, XlSaveAsAccessMode.xlExclusive,
_missing, _missing, _missing, _missing, _missing);

           ReleaseComObject(sheet1);
           book.Close(false, (object)_filename, false);
               ExcelApp.Workbooks.Close();
           ReleaseComObject(book);
           ReleaseComObject(books);
               ExcelApp.Quit();
           ReleaseComObject(ExcelApp);
           GC.Collect();
           GC.WaitForPendingFinalizers();
       }
       private void ReleaseComObject(object ExcelObj)
       {
           try
           {

System.Runtime.InteropServices.Marshal.ReleaseComObject(ExcelObj);
           }
           finally
           {
               ExcelObj = null;
           }
       }

   }
}

Regards
Senthil