The Device Id field is key to making your WS appear 'registered'. This can be done only through the control-panel.
However, the registry.new file was the rosetta stone for cracking the WS ... thanks diverse :)
Here are the steps to hack a virgin (as in unmodified) Websurfer to use your own ISP.
1. Connect everthing. Go through registration screen and provide information.
2. Be sure to choose "I'll use my own ISP" option.
3. In the next screen, enter all the ISP parameters. Set up atleast one user.
4. Now, hit Ctrl+Alt+M
5. In the pop-up box enter f1n9eR
6. You are in the Control Panel.
7. Change all *.websurfer.com URL in all the screens to something else (preferrably your own server, so that you'll know when the WS is trying to call home).
8. Go to the other settings screen
9. Change the Device ID from 0 to a non-zero number (e.g 1234)
10. Power off the WS and power back on.
11. You should now be past the registration screen.
12. Say YES to "Are you still using this number .... ?" question (if asked)
13. Choose a User, modify ISP settings if necessary and dial-out.