Modifying MsDtsSrvr.ini.xml - Receive "Access is denied." error upon saving.

I wish to make a change to MsDtsSrvr.ini.xml in order to add another directory for the "File System" packages. However, whenever I go to save the file after making the change, I get an "Access is denied." error. I have tried stopping the Integration Service, but that still does not allow me to save the updated MsDtsSrvr.ini.xml file. Please advise...