JSI Tip 1541. You can't download a 128-Bit Service Pack?

Even though you are located within the United States or Canada, you receive the following message:

Your computer does not have a Domain Name Service registered for it. We are unable to determine the physical location of your computer. You should contact your system administrator to find out why a DNS entry is not registered for your IP address. A DNS entry is a requirement for downloads at this time.

Chances are that the DNS server that is SOA (Start Of Authority) for your reverse lookup zone does not have a PTR record for your computer. Thus, Microsoft can not resolve the IP address to a domain name and verify it is within the United States or Canada.

Have your ISP create a PTR for you in the appropriate reverse lookup zone, or have the ISP grant you SOA for your IP address range so you can maintain a reverse lookup zone.

See Q172953 - How to Install and Configure Microsoft DNS Server.