Free XML parsers are readily available for example as part of the Java or .NET platforms. There are also plenty of good XML editors, which will give you access to an XML parser. Products like Stylus Studio, XML Spy, and Oxygen do a lot more than just editing and parsing. I suggest you search around to find the tools that meet your need - the information is readily accessible.
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference