I use a very fast installation method for don't lose all module installed on my last DNN installation:

1) Copy entire DNN directory in another

2) Give right access to the folder

3) Build the IIS application for the new copy

4) Change the Sql express DB name

5) Change the name of renamed DB in the Webconfig

6) Lunch the new site with a previously created alias

7) Delete all old existing portal

I use this method with excellent time saving!

There are no problem working in this way? I'm no expert, and I'm not sure It's right.

The only thing I'm in question about this, is around the same ApplicationId I've in different DNN installation

What do you think about this? 

Yes, you understand right. I've talk about SQL Express DB name because in my installation I link to DNN DB trough the SQL Express instance and not directaly to DB file.

So, in your opinion, you don't see any problem? then, which the difference to have the same or the different application id for different DNN installation?

(In this moment I've six different DNN installation in this way working with no visible problem)

Thanks