Character who start TTW with previous NV save file( without TTW ) will also receive letter from dad.
After read the message, prompt up a option menu which allow player "flash back" and start first four quests. Upon exit Vault 101 door, store items in a footlock outside the door and move character back to the place where he/she flash back.
I really hope I can start F3 main quest from the very beginning on my save file...