<p>How do I generate excel reports with rich formatting including charts with a ASP.Net application?</p>

<p>As per <a href="http://support.microsoft.com/kb/257757" rel="nofollow noreferrer">http://support.microsoft.com/kb/257757</a> server-side automation of office is not advisable and also our admin does not allow installation of office on the server</p>

<p>Customer is not ready to spend a lot on 3rd party components</p>

<p>A must requirement is to retain the formatting used by the end user already and also use ONLY excel 2003.</p>

<p>Thanks</p>

<p><strong>Update:</strong> We are using ExcelXmlWriter from <a href="http://www.carlosag.net/Tools/ExcelXmlWriter/Generator.aspx" rel="nofollow noreferrer">http://www.carlosag.net/Tools/ExcelXmlWriter/Generator.aspx</a> as it was the most fit.</p>

Two options you might consider:
1) The ReportViewer control.  You can design your report, including charts, and have it output to excel.  You can allow the report to be shown within the control, or bypass that and export it directly to excel.  The version it will be open in depends on what the client has installed.
2) You could create a page that with the lay out you are seeking using a GridView, or plain old HTML tables with your chart images embedded.  Modify the response headers so this page downloads as an excel file.
If you need to preserve Excel charts that change when data is changed in the resulting Excel file, I'm not sure if that is possible without the use of third party controls or Office automation.  The options above work if you are embedding a chart image created by your asp.net app.