I have installed SPS 2003 on a single machine. I have created the portal
site (Default web site virtual server) and all seems to work. I can access
Portal Site "Site Settings" menus, add existing myDomain\myUser and giving
them Administration permission to the portal. The problem is when I go to
the Portal Site root ( http://myServerName/ <http://myServerName/> ):
Sharepoint do not recognize the Domain\User I provide with the appropriate
password. (The one I added above)

I cannot access this portal web site home page with any of the users I have,
even the one I used to install sharepoint nor the one used by IIS (admins
users). I don't have installed Active directory and I also followed the
steps wrote by Microsoft for installing my SPS 2003.

Is it a known issue? Somebody can show me possible solutions to check? (I
made a lot of checks already.)

I use windows Server 2003 Standard Ed. with SQL Server 2000 Standard SP3a