Phil, I'm sorry but you won't be able to do that with the current setup, you have to 'restart' the game.

To do that redownload or recopy over the walkthrough folder to where it goes in your Dom2 folder and restart the game.

http://www.maladjustite.com/dom2_walkthru.html

Redownload the link saying "walkthrough.zip" and reinstall it. It will probably ask you to overwrite the game and you should probably say "Yes" then after that is done, go through the initial walkthrough steps in order to start the game.

If you just want to start with the same Pretender/Race in the game that you had, you just have to create a game with Jotunheim as Human and it will upload that pretender unless you've tried to create another one since you've installed the walkthrough.