Frontpage Subwebs - Search engine implications?

I am planning to split my site into subwebs - a good idea?

[Chris27]

My Frontpage site has subsites with their own domain names. At the moment these are subfolders and not subwebs.

I am planning to split my site into subwebs. I want to restrict Google to only index the pages that belong to each web for the appropriate domain.

At present, by having different domain names (which ARE needed) I'm concerned that the search engines are finding the same content from the different domain names and may think this is duplicate content, when it is really a useful site which needs different domain names for the different parts. (subdomains would not be appropriate).

Will using subwebs stop the search engines crawling around the folders outside the subwebs?

Are subwebs a good idea?

Your help is appreciated