How to Verify that the TCP/IP Protocol is Installed (Earthlink DSL for Windows 98)
If the TCP/IP protocol is not installed in the Network section of the Control Panel Error 645 can occur.
Verifying that the TCP/IP protocol is installed
Click the Start button, click Settings, and choose Control Panel.
Double-click the Network icon.
Click the Add button.
Note: If TCP/IP is already installed then try other resolutions. If there is more than one TCP/IP listed and there is no TCP/IP -> Dial-Up Adapter then proceed with this resolution.
Select Adapter in the list.
Click the Add button.
Select Microsoft in the Manufacturers list.
Select TCP/IP in the Network Protocols list.
Click the OK button.
Click the OK button.
Note: If prompted, insert the Windows CD-ROM or point to the location where the cabinet files are stored
Click the Yes button if prompted to restart the computer.
When the computer has restarted, try connecting to the internet again.