Here's what I get when I try to install WordPress in the root directory of  (what I'll refer to as) "addondomain.com":

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Install WordPress (2/3)


The installation can not be completed:

- You cannot install more than one script in the root directory of a domain.

Click on the browser's Back button to fix reported errors.

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I haven't got any other scripts installed in the root directory for this domain. This is an add-on domain; would that affect anything?

I *am* able to install WordPress if I choose to install it in "addondomain.maindomain.com" instead of "addondomain.com".

I am also able to install WP in any SUBdirectory on the addon domain (e.g., "addondomain.com/blog").

Any advice?

Thanks very much....

Please check this article for the solution;
http://wiki.lunarpages.com/Fantastico_Troubleshooting

If you cannot get it working, please feel free to email support@lunarpages.com

Wordpress has specific files that if you try to install another copy, some would overwrite the others. You need to make a subdomain or directory to install it to instead. If you wanted though, you could always go through and rename a lot of the files then re-link them, but that's a waste of time when you could just do a subdomain. Why would you want 2 installations of the same script in the root directory anyway... that doesn't make sense to me.