I have a ASP.NET 2.0 web application that should upload a ppt file and then extract its slides to images. For that I have imported office.dll and Microsoft.Office.Interop.PowerPoint.dll assemblies and wrote the following code

public static int ExtractImages(string ppt, string targetPath, int width, int height)
    {
        var pptApplication = new ApplicationClass();

        var pptPresentation = pptApplication.Presentations.Open(ppt, MsoTriState.msoTrue, MsoTriState.msoFalse, MsoTriState.msoFalse);

        var slides = new List<string>();

        for (var i = 1; i <= pptPresentation.Slides.Count; i++)
        {
            var target = string.Format(targetPath, i);
            pptPresentation.Slides[i].Export(target, "jpg", width, height);
            slides.Add(new FileInfo(target).Name);
        }

        pptPresentation.Close();

        return slides.Count;
}

If I run this code in my local machine, in asp.net or a executable, it runs perfectly. But If I try running it in the production server, I get the following error:

System.Runtime.InteropServices.COMException (0x80004005): PowerPoint could not open the file. at Microsoft.Office.Interop.PowerPoint.Presentations.Open(String FileName, MsoTriState ReadOnly, MsoTriState Untitled, MsoTriState WithWindow) at PPTImageExtractor.PptConversor.ExtractImages(String caminhoPpt, String caminhoDestino, Int32 largura, Int32 altura, String caminhoThumbs, Int32 larguraThumb, Int32 alturaThumb, Boolean geraXml) at Upload.ProcessRequest(HttpContext context)

The process is running with the user NT AUTHORITY\NETWORK SERVICE. IIS is configured to use anonymous authentication. The anonymous user is an administrator, I set it like this to allow the application to run without having to worry about permissions.

In my development machine I have office 2010 beta1. I have tested with the executable in a pc with office 2007 as well. And if I run the code from the executable in the server, with office 2003 installed, it runs perfectly.

To ensure that there wouldn't be any problems with permissions, everyone in the server has full access to the web site. The website is running in IIS7 and Classic Mode.

I also heard that Open-office has an API that should be able to do this, but I couldn't find anything about it. I don't mind using DLLImport to do what I have to do and I can install open-office on the web server. Don't worry about rewriting this method, as long as the parameters are the same, everything will work.

I appreciate your help.
ps: Sorry for bad English.