Ok, sorry I had gotten busy on other things.

Basically you have an side by side upgrade and you want the server names and instance names to be the same in the end. Right?

I have done this on windows 2008 r2, and this is roughly how I did it.

Build your SQL 2008 cluster with the same instance name as the SQL 2005 box, virtual name is unimportant since it isn't gonna be the final.

Do your upgrade.

Rename to virtual name of the SQL 2005 cluster to anything other than its name now. Change the IP address in the resource group to some other IP address. I would probably take the resource group offline.

On the SQL 2008 box change the virtual name to the name of the old SQL 2005 cluster, then change the ip address. I would probably set the port for SQL to the same as what the old SQL 2005 was using. Stop and restart SQL, it should now be using the new IP and virtual name.

You should now be able to decomission the SQL 2005 box on whatever timeline you want. Once that is done you will have to clean up the AD since the virtual name that the SQL 2005 box was using is not deleted.

CEWII