Well, somehow, yesterday when I tried to download from MSDN the latest version of Windows 7, Enterprise was showing as available. I always pick the highest one on the list so I chose that and started to download. It did not finish, and when I started it again, I noticed it did not show again. Frustrated, I posted to my twitter feed that maybe Microsoft had run out.
It went to my facebook, and Steve Evans posted on my wall saying that I really wanted Ultimate.
He also included this link to describe the differences.
http://en.wikipedia.org/wiki/Windows_7_editions
Thanks Steve.
Hope this helps.