var xmlDoc = new ActiveXObject("Msxml2.DOMDocument.6.0");
var nodeBook, nodelistAuthor;
xmlDoc.async = false;
xmlDoc.load("Lab.xml");
if (xmlDoc.parseError.errorCode != 0) {
    var myErr = xmlDoc.parseError;
    alert("You have error " + myErr.reason);
} else {
    nodeBook = xmlDoc.selectSingleNode("//dvd");
    nodelistAuthor = nodeBook.getElementsByTagName("название");
    alert(nodelistAuthor.item(0).text);
}