Can I run multiple installations of a WordPress blog on a single virtual dir?

Can I run multiple installations of a WordPress blog on a single virtual directory and database?

I use Brinkster as my host and already have 1 WP blog set up. Can I upload WP to another folder to set up a second blog on the same account?

It is single virtual directory and database.
I assume each instance of WP would need to have its own prefix in the table names?

Please help.
Thanks,
Dave