We have two computers running Windows 2000 Server, connected to the Internet using Internet accounts from two different Internet service providers. The IP addresses are provided dynamically by the ISP -- i.e., the IP address is not permanent or reserved for us.
As we are aware of those two IP addresses, can we establish a VPN channel between the two machines as long as the Internet connection is maintained with the ISP? If so, is it possible to do the same even though we have the two Internet accounts from the same ISP?
Yes, you should be able to do this. The fact that the accounts are from different ISPs won't affect the VPN connection. The use of dynamically assigned IP addresses does make this more difficult, however. There is no perfect way to find systems with dynamically assigned IPs. However, a good start is to set up DNS hostnames for both systems, and configure your DNS provider to automatically update the DNS hostnames when the IP addresses change. Most free DNS providers on the Web support automatically updating DNS records. I use zoneedit.com, but you can find many such providers by doing a search on the Web.
While dynamic DNS may be your best low- or no-cost solution, you will probably experience some downtime when an IP address does change. It can take several hours for DNS updates to propogate.