c:\Whatever.html as a URL in the HTML window does work if the file exists, as does the http URL for a local webserver
You should be able to embed the log data into a textbox with a simple XML include. Considering how long the file is likely to get, anything other than a scrollable textbox is probably impracticle.
You can of corse pre-parse the data into an XML format for other types of display. For instance, its possible to build a Journal style colapsable tree view.
However, there isn't an easy way to do lookups across datasources. Showing details matching a selection in the tree view is a problem. Likewise, showing HPs for a targeted mob is a problem.