How do I hide the “root” domain name…

I registered two domain names, e.g. “www.domain.com” and “www.otherdomain.com”. At my webhosting service, “domain” is the “root” domain and “otherdomain” is a subdomain.

I’m running WordPress from the directory “/otherdomain” and it works just fine. When I go to “http://www.otherdomain.com” the blog comes up, no problem. However, when I look at the source code, the full URL “http://www.domain.com/otherdomain/” shows up.

How can I reconfigure WordPress so that the only URL that appears in any source code is “http://www.otherdomain.com/”

Bottom line is I don’t want the blog to be associated in any way with the “root” domain or website “http://www.domain.com”