Not really! i myself am a newbie at this
ne way ... NO would be the answer to your question as I understand you are talking about the Username & Password asked when open the link to the main forum page in a seperate Windows Login window. Because in my best knowledge that is set from IIS (Internet Information Server) on a webpage. If you have the administrative rights of the webspace you have you may remove it, if not then call the web hosting company and ask them to do so.
now the admin area you reached, it has forum settings from there after removing username password, u can set passwords to access the forums only, not the defalt.asp file, then set the forum permissions for registered users only so that no guests can post,view or do anything in them.
that i think sums up almost everything. still not sure what to do, simply post the query. if not me someone else will get u out of this.