Does the CD from the 1st one not work with this one? At the end of the day you did buy it and you are only using it on 1 computer so I can't see how your violating the license.
Another quick workaround is to remove the product id from the PID.txt in the Sources folder on the DVD drive (you will need to extract to a temporary folder and re-burn to a DVD do this), once done simply select the version you want in the Vista setup, it will install and give you 30 days to activate. Now simply buy a license when it prompts
You are not doing anything illegal here and it means you can get working much faster without having to wait for another DVD to arrive in the post.
Hope this helps, Chris.