As David says, unfortunatly you have to enter in the whole URL for the pages to be found. If however you're wanting to slim down the link so that it shows as metroppo.html instead of http://ethanwain.com/metroppo.html then you can add the following code to your page.
HTML Code:
<a href="http://ethanwain.com/metroppo.html">Metroppo,Html</a>
You don't have to purchase a whole new account. All you need to do is purchase the second domain name and then add it to your main account as an addon domain. See how here.
By having an addon domain, it does not mean people will know the second domain is connected with your main one. i.e. your main account is ethanwain.com and your second is Sitebuildz.com no one will know that you own both accounts unless you tell them.
As an example of how this works, check out my domain Globalmook.Com and my addon domain Freeresourcedirectory.com in my sig below. Now if i hadn't told you would you know that they are both on one account??