ASP Application - Excel Export

We have an ASP 3.0 application that uses SQL 2005 for the database.  One feature we have is that ability to export database records to an excel spreadsheet.  For example a user will be on a page and click export records.  A window will pop up and prompt them to save or open the file.  If they click save, it saves to the desktop (or any location they save it to) very fast.  The file itself is only 2.5MB.  It has about 4,000 records and about 50 columns of data.  We think there is no problem exporting the data to excel as the file saves very fast.  However, when you try to open the file, it can take up to 5 minutes to open.  Excel just hangs as it is trying to open the file.  The file itself is not very big, but we think this may be because when the file is exporting to excel, it may be exporting all HTML in the background (not sure if that is correct though).  We are just using standard ASP 3.0 code to export that data.  Can someone please suggest the best method for exporting this file to excel without the issue we are having.  It still must be done in ASP as the applicaiton is an ASP app.  

Thank You --