2nd WordPress install in root with current install in directory

Hi all,

I’ve just read some information on the options for Multiple Blogs, but I still have a doubt that I’d like to resolve before I venture into this…

My situation is this:
– I currently have a non-wordpress php business website.
(i.e. http://www.domainname.com)
– On the same provider server, I’m running a personal photoblog in WordPress, installed in a directory photo (i.e. http://www.domainname.com/photo, which is also available through the subdomain my.domain.com).

This is what I want:
– Convert my business website to WordPress, keeping it in the root, so no subfolder is displayed in the browser (i.e. continue to be http://www.domainname.com and not for example http://www.domainname.com/business)
– Maintain my personal photosite in the personal directory.

Problems:
I am looking into the options for multiple Blogs.
It seems I can’t either of the new Create a Network options:
I can’t choose Sub-domain Install because WordPress is currently installed in a directory.
Also, I can’t use the Sub-directory Install because my existing WordPress installation has been set up for more than a month.

Solution?
Is the ‘old fashioned’ Multiple Blogs Through Multiple Installs my only option? My provider allows multiple databases, so I should be able to set up a second database for the business install

If so, can I install a second copy of WordPress in the main directory?
Will my original WordPress install in the subdirectory still work?

Or should I rather install the second copy into a directory also and change settings so this directory is not displayed to people visiting the business site?

Thanks you any light you can shed!