Producing Excel files in ASP on IIS7.5 - excel

Question

On an existing web application I support there is a page that is used to produce an Excel spreadsheet for some data. The Web server has Excel 2002 installed (so old...) and makes uses of automation of the Excel object to do the work.
I am fully aware that automating Excel like this is not recommended by Microsoft, but this is the way is currently works, and I am never allocated any time to look to change this.
Here is some sample code
Dim xlApp, xlBook, xlSheet
'create the Application Object and workbook object
Set xlApp = Server.CreateObject("Excel.Application")
Set xlBook = xlApp.Workbooks.Add
Set xlSheet = xlBook.Worksheets.Add
'turn off any alerts
xlApp.DisplayAlerts = False
xlApp.Visible = False
xlApp.ScreenUpdating = False
xlApp.DisplayFormulaBar = True
xlApp.CommandBars("Standard").Visible = True
xlApp.CommandBars("Formatting").Visible = True
xlApp.CommandBars("Chart").Visible = True
xlApp.CommandBars("Control Toolbox").Visible = True
xlSheet.Cells(1, 1).Value = "Test"
xlApp.ScreenUpdating = True
xlApp.ActiveWorkbook.SaveAs ("C:\Temp\Test.xls"), -4143
xlApp.Quit
Set xlApp = Nothing
The Web Server is a Windows 2003 server, running IIS6, and everything works happily. However, we are currently upgrading to using Windows 2008 servers, running IIS7.5 and the above code is no longer working. The message returned is as follows:
Microsoft Excel error '800a03ec'
SaveAs method of Workbook class failed
xxxxxx/Test_Excel.asp, line 42
The thing is, is that if I create a simple .vbs file, with the above code and run it, it all works as expected. It is only when running as an ASP page does it fail.
The folder is it trying to write to should have the correct permissions (I added 'Everyone' to it, with full access).
Does anyone have any suggestions as to why this is happening?
Thanks!

Answer 1

First of all I'd remove that Everyone group from the folder you're trying to write to, that's leaving open a potential security headache for another day.
There's a few different ways that your site could be configured to authenticate which will determine the identity that the Excel COM server will launch as.
However, rather than go through them all, create a script that does just this:
<%
Dim xlApp, xlBook, xlSheet
'create the Application Object and workbook object
Set xlApp = Server.CreateObject("Excel.Application")
Set xlBook = xlApp.Workbooks.Add
Set xlSheet = xlBook.Worksheets.Add
%>
Open task manager, select the "Processes" tab. Ensure that "Show processes from all users" is enabled and sort the processes by Image Name.
Browse to the script above and you should see the Excel.exe appear in the process list:
In the third column you will see the identity that Excel is running under. That's the account that needs write permissions to your c:\Temp folder.
When you do this you'll need to manually kill Excel.exe because it'll just keep running otherwise.

Answer 2

The only thing I can recommend is to check your App Pools in IIS7. Within the Advanced Settings of the App Pool, you may have to change the Identity account to one of the built-ins. By default in IIS7.5+, a dynamic account is used with the name of the App Pool and it appears in your Task Manager with the name.