The XML file is used by major applications where I work for, and is not going to change for my new app.

Does that mean that they are not using XML parsers either? This is a Bad Thing:

• These apps may not be following the XML standard exactly right. This would mean that you have files which look like XML but are actually not, so they cannot be parsed by a real XML parser.
• Or the XML files may follow the standard exactly right, but the input code makes invalid assumptions about the form of the XML. At some point in the future, a programmer who believes she is dealing with an XML file may make a change which produces valid XML data, but it cannot be read by your parsing code.
• Because of both of the above items, you are not reaping the full benefits of using XML - a standard format for data interchange. Even if all your apps work together to support your own brand of not-exactly-XML-but-close, other apps should be able to create XML that you can read, or read XML that you created.

If your new app does not use an XML parser either, that only contributes to the existing problem. It will need to be updated if the input file changes in format.