If using Exchange 5.5 you can choose between an NT or Windows 2000 fax server.
Serial number is the same for both.
Competitive product must have been purchased within the last 2 years. On all products a maintenance agreement is highly recommended. This will give you free software updates, as well as support during office hours. Without maintenance agreement, support is free for a period of 3 months after purchase of the product. Standard phone and email support during office hours.