Two in one

Hi.

I have two blogs that I would like to keep separate because of the content, but I want to be able to have it under ONE domain using the same themes, the same navigation, etc. I want to be able to post in there as if I was posting in my main blog, but I do not want to have to upload everything to the new subdomain. I am not sure you understand what I am talking about, but if you do, can you tell me if this is possible and how to go about it?

Maybe this will help:
voltage.nu is my main blog
voltage.nu/rant is my ranting blog
I want /rant to work under the same wp-content as the main blog.

Haha, if that did not help, I am sorry.
Thanks again.

Roxanne.