TinyXML can't read some files

Question

I can load a file applicationHost.config

<Parent>
    <Child1 test="program" />    
    <Child2>
        <Node number="123456789" />      
    </Child2>
    <Child3>        
        <Hello World="!!!" />
    </Child3>    
</Parent>

just fine in one folder C:\Users\Public\Documents\temp but if I move that file to another folder C:\Windows\System32\inetsrv\config

I get a "Failed to open file" with erroreRow=0 and errorCol=0

Code snippet:

    std::string fileName = "C:\\Windows\\System32\\inetsrv\\config\\applicationHost.config";
    //fileName = "C:\\Users\\Public\\Documents\\temp\\applicationHost.config";

    std::string output;
    TiXmlDocument doc;

    if(doc.LoadFile(fileName))

As you can see I am using an absolute path, so there shouldn't be any worry about relative directories. Also, the file in both instances have read-only UNCHECKED, and users set to EVERYONE with full control on.

Why can't I load the file when it's in C:\\Windows\\System32\\inetsrv\\config\\applicationHost.config