Hi,

1. The web site will run OK with IIS 7.0 on Vista but complies with the above error.
    
2. The site is also on a Win XP Pro machine where it runs OK with IIS 5.1 and also complies with VS 2005.
    
3. I transferred the site to Vista from the Win XP Pro machine without change and using the same web.config. I am using SQL Server 2005 in both places. I backed up the database on the XP machine and restored it on the Vista machine. 

Just to eliminate an impossibility, I know for a fact that I was able to compile version 4.05.04 on a machine running vista with IIS 7.0 and VS2005 SP1; which whatever service packs and windows updates that existed at the time that 4.5.4 was released.

I would consider upgrading to 4.8.0 first, so that you can use the default web application in iis 7.0.  The only upgrade issue that might concern you is that if you use the active directory authentication provider, it is broke in 4.8.0.

I generally make it a habbit to upgrade all of my dnn installations (about 40 of them for 6 different companies) within a month of its release (after being able to test it, obviously).

If you're new to the game; you should be aware that you should only be using the DotNetNuke source if you've run into debugging issues that require you to step through the code, or for education / research purposes.  If you're just developing modules or extensions, you should consider developing them against the install package; you'll save yourself a lot of headaches.  You should also *never* consider changing the core code as a way to implement functionality; there is always a way around it.  The only time that you should consider changing core code is to implement a bug fix pre core release....  If you don't follow this advice you're in for a lot more headaches when it comes time to upgrade.