Code:
        Dim doc As New XmlDocument
        doc.Load("C:\Documents and Settings\p068612\Desktop\DVD.xml")
doc.GetElementsByTagName("DVDInfo")
        doc.CreateElement("DVDTitle")
        doc.InnerText = Me.txttitle.Text
doc is your XML document. You want to set your InnerText property of your element, not your entire XML document.

Here are the examples you are looking for:
http://msdn2.microsoft.com/en-us/library/fw1ys7w6.aspx
http://msdn2.microsoft.com/en-us/lib...innertext.aspx

This may perhaps be helpful as well:
http://www.vbforums.com/showthread.php?t=478692