DotNetNuke: Object reference not set to an instance of an object.

I am trying to install the DotNetNuke Community Edition. When I first ran the installation, it brought up the Install Wizard. I proceeded through the screens until I got an error message I couldn't decipher at firt.
I then ran the install again and got a "Not enough storage space error. So I deleted unnecessary files and added extra disk space.
I then ran the install again and got the "Object reference not set to an instance of an object." message.
So I next I deleted the DoteNetNuke folder from the web server and republished it. When I ran the install again, it still displays the "Object reference not set to an instance of an object." message. I had expected the wizard to run again so I could get it to run to completion. I have no idea where to go from here. I have checked the DotNetNuke Forum for the "Object reference not set to an instance of an object." message and cannot find a situation similar to mine.
David Hynes