I have the following code:

 public void BeginConvert(object data)
 {
 ConverterData cObject = (ConverterData)data;
 string argument = string.Format("-i \"{0}\" -b {1} \"{2}\"", cObject.Source,    compression, cObject.Destiny);

 Process converterProcess = new Process();
 converterProcess.StartInfo.FileName = ffPath;
 converterProcess.StartInfo.Arguments = argument;
 converterProcess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
 converterProcess.Start();
 converterProcess.WaitForExit();
 }

I use it in a webservice, i start it in a new thread and it return exit code 1 (error, i'm trying to do a video convertion with ffmpeg library), i impersonate ASP.NET to use a local account with permissions to read and write files, when i run it in my machine running or debugging it works but know thta the web service is running in IIS doest'n. Could someone help me?