Hey Mike. . .
I've discovered a couple of things since the original post.
1) Although ASP.NET 2.0.XXX showed up as installed, it apparently had not registered with IIS (wasn't showing up under IIS Web Service Extensions. I found this article ( http://office.microsoft.com/en-us/winsharepointadmin/HA100598511033.aspx ) which helped resolve the problem.
2) I setup DNN v4.5.3 on a webserver, but when I tried to access the site to run the Installer from a machine sitting out on the internet using the actual domain name, the InstallWizard would would startup but (first clue) no images, like the left or right arrows, would show up. I could proceed to test the file permissions (responded that permissions are OK), then move on to test the database connections, which also tested correctly.
The whole thing fell apart when I got to the page where the database scripts run. The progress bar would indicate something was happening but no scripts appeared in the window where installation success is reported. Everything would hang right there. I suspected there was some kind of a file permissions problem. In setting the permissions for my D:\Website folder, I copied the permissions on the C:\inetpub\wwwroot folder and added full control for NETWORK SERVICE. When you run the install locally, everything goes as you would expect, however, even after adding a Portal Alias, when you try to access the site from the Internet, the browser indicates it's trying to load either localhost or, if the Installer ran under an internal address, the internal ip address.
Any ideas?
Warren