If you recieve the following error;
HTTP 403 You are not authorized to view this page

What you need to do to resolve tihs is the follwoing steps

In your global.asa check the the database path is correct, by default the portal will try to auto detect this if this fails then you will get this message.
Simply replace this section in your global.asa;
" & server.MapPath("../data/aspportal.mdb") & ";

With

c:\portal\data\aspportal.mdb
or the actual physical path to the database, also make sure the ISUR has read and write access to this folder.