advanced forums

Hi Folks,
I am developing D7 multisite using Domain Access module. I am able to import all user from their current site (which is not in Drupal) using Uif and uif_plus module. Now i want to migrate their current forum i.e. JForum into Drupal forum. How i can do this? if any one did this before if yes than please tell me the possible solution ? i don't want to lost any post or data or comments.

Thanks in advance.

What are the pros and cons for using Drupal Advanced forum or phpBB?
demo of Drupal Advanced forum is here: http://shellsn.com/forum
this demo used Blue Lagoon Stacked styling
how to style your advanced forum is here: http://drupal.org/node/234042

For a good example of using phpBB with Drupal 6, see here:
http://www.teenrc.ca/phpbbforum
you can download phpbb skins from the internet
Drupal has module for phpbb. drupal.org forums has a drupal 6 version

I like the style of phpbb for the posts with the author pane on the right hand side.