Are you using third party or custom system (e.g. a CMS, forum, blog) for your website? If third party, which one? Chances are you need to reconfigure that. Your best bet is to leave the server name out of links, if possible.
Are you using a CMS or are the pages hand coded?
Seems the URLs are hard coded to the full path instead of relative. You will just have to change them, from
subdomain.x10hosting.com/register.php
to
/register.php
(assuming that by "pointing to" you mean you parked it on top of your x10 account ).
I'm using a forum.
Are you using third party or custom system (e.g. a CMS, forum, blog) for your website? If third party, which one?