What is Dynamic DNS?
(Definition from wikipedia.org)
Dynamic DNS is a system which allows the domain name data held in a name server to be updated in real time. The most common use for this is in allowing an Internet domain name to be assigned to a computer with a varying (dynamic) IP address. This makes it possible for other sites on the Internet to establish connections to the machine without needing to track the IP address themselves. A common use is for running server software on a computer that has a dynamic IP address, as is the case with many consumer Internet service providers.

What is the difference between the desktop and service versions?
The desktop version requires the user to manually start the program or place it in their startup group to have it start upon login. The program only runs when a person is logged into the computer and the program is either in the system tray or on the desktop. The program will stop running once a person logs off the computer or manually shuts it down.  The service version is a true Windows service. It will automatically start each time the computer boots up and will continue to run until the computer is shut down. It does not require a person to be logged into the computer for it to work. The program also does not require that the user interface be running on the desktop or in the system tray. Overall, the service version is the better choice if you can run it. It requiresWindows XP or newer.

Will the Dyanmic DNS Client run on Windows 7?
Yes

I enabled the background, but it doesn't seem to do anything?
The background option will display a colored background on your desktop with your computers name and IP address printed in the lower right corner. You must select both a font color and a background color for this to work. If you leave either of them at their default you may not see the background change. The background will be updated when the client detects an IP address change. If you are using the service version, you must have the client's user interface running for this feature to work.

I purchased version 1.x of the Dynamic DNS Client.  Can I upgrade to 2.0?
Yes, however you will need to purchase a new license.  We offered free upgrades to all users for several years during the 1.x versions lifespan.   We have spent a considerable amount of time updating the software and adding features for version 2.0, therefore we cannot offer free upgrades from 1.x to 2.0.

If I purchase 2.0 will I receive free upgrades?
If minor updates are made to version 2.0 those will be provided to licensed 2.0 users free of charge.