If you already have a Vista install dvd, no need to join msdn just for that.
You can use any MS Vista dvd to install any edition of Vista.
No modification needed.
Whatever edition key you enter will be the edition that is installed from the dvd.
If you skip entering the product key, ( untick activate automatically online ), you will be presented with a list of the Editions.
Install any one you want - you then have 30 days to insert the product key.
In that respect the Vista install dvd is better than the 7 install dvd.
To be fair to MS, I believe they locked the 7 install dvd's to one edition to make it easier for people - so they don't accidentally install an edition they don't have a key for.