Need help understanding AdobeID, completely confused!!

So I registered CS5, with my email address.  I wanted to use a new email address so when I went to adobe dot com, under adobeID i changed to the new address.  After that under product registration it doesn't show CS5 anymore, I thought that maybe it was only linked to the old email address as the adobeID so I changed it back but it still didn't show up.  I then processed to change the id to something else and create a new account with the old info, the product registration was back, I should have stopped there but I decided to give it one more try and its gone now, and I have an extra account on adobe that I don't know how to get rid of.  So my quetions are:

How does the registration connect to adobe products (specifically in my case it would be photoshop CS5)?

Can I change the AdobeID or email address its connected to (the email address its currently connected to is to my ISP which I am changing soon)?

How do I close an adobe.com registration that doesn't have any products connected to it?

Anything else that I should know?

Thanks in advance for all your responses.