Small issue with the following. It works, but when the File Download window pops-up and I click on "Open" another (almost) exact pop-up appears. The only difference is that the "Always ask before opening this type of file" checkbox at the bottom is not grayed-out on the second one. The second one will actually open the download file. The first one works as exepected if I click on "Save" or "Cancel" so why would clicking on "Open" cause the second window to pop-up?

Response.AddHeader("Content-Type", "application/ms_excel")
Response.AddHeader("Content-Disposition", "attachment; filename=Principal_Download.xls")
cOutput = m.ExcelData
Response.Write(cOutput)