Problems in generating XML

I'm using System.xml to generate custom XML. 
When I generate the xml with a custom header it creates a special character at the beginning of the file. I can only see this character when I open the EDIT Command in Windows. Has anyone experienced the same problem epode help me? 
For this character prevents me process this file in SAP. Every time I need to process, need to open again via EDIT Prompt Windows to delete this special character at the beginning of the file.