I am sure others have tried this but here's something interesting..
I took a look at the information that the Modem was using to get the update. The POST and URL fields and put together a quick web page to grab the data..
<FORM METHOD="POST" ACTION="https://webcdownload.msn.com/clientman/clientman.dll?DownloadImage">
<INPUT TYPE="text" name="CurrentVersion" value="0"><BR>
<INPUT TYPE="text" name="Component" value="Mariner;Compaq-1-1;409"><BR>
<INPUT TYPE="text" name="SSN" value="1"><BR>
<INPUT TYPE="submit">
</FORM>
What I recieved was a binary file which i will be inspecting to see if I might glean any info about disabling the MSN Login Requirement.. But I doubt that it will be fruit full. Happy hacking