Dynamic pages (forum archive) move, what to do against duplicates?

Moving my well listed forum archive to another place, using another script

[MartijnH]

We currently have a website www.domain.com with the forums at subdomain.domain.com and the spiderable archive of the forum at subdomain.domain.com/archive. We are probably the largest forum on our subject with over 60.000 threads, most of them on the subject, so I really like to have our threads in Google.

Now I found out that the script for the archive, which we are currently using, is certainly not the best and I found a better one. However the readme says it will work best with www.domain.com/forum/archive. I want to create a www.domain.com/archive (because all data comes from a database so it's no problem to have it outside the forum directory) and also add the archives of our newspage to it.

But this raises several questions:

1) Our domain has a very stable PR7, is there a chance Google will ban/lower the entire PR of the site because I move the forum archive to a directory? (I think Google seems not to like forums at this moment).
2) What should I do with the old archive? It is well listed, but as the content from the new and old archive will be same (only the layout and URL will change) will Google consider this as spam?
3) How would you recommend me to do the move, I don't want to lose all results in G, nor do I want to be banned...

[MartijnH]

I'm really looking into any replies, still have a big need to make changes, but not sure if I will bring the Google ranking in danger..

[seoRank]

1. Short term view - If, as per you, Google has not indexed most of the content, then you do not run the risk of Google banning you for identical content since it does not know the other one exists.

2. Long term strategy would be to phase out the old directory and handle it by proper redirection. Avoid keeping duplicate content, just in case Google decides to see the old one too.