Multi Site Install Document Root for each domain?

Hi all, got a question re: Multi Sites and the domains...

I've set everything to work fine as http://example1.com/site2

But am now trying to get it to display as http://site2.com ...

I can't figure out where to point the document root for http://site2.com! Can anyone help?

I've tried this:

site-root:
Name VirtualHost 111.22.33.444
DocumentRoot /absolute/path/to/drupal
ServerName site-root.com

site-one:
# note that the DocumentRoot is exactly the same for both VirtualHosts
DocumentRoot /absolute/path/to/drupal
ServerName site-one.com

subdomain.site-two.com:
# note that the DocumentRoot is exactly the same for both VirtualHosts
DocumentRoot /absolute/path/to/drupal
ServerName subdomain.site-two.com

And it displays the first page fine. However, when I try to click on any other page, it gives us a 404 error.

Any ideas?