Is it possible to remove an email address from a previous account trial?
The answer to this is: sort of.
There is not a way to delete the previous account, however, you can sign in with the previous email address, and password here:
Then click 'My Settings' and then change the email address to something that looks like this:
This change will free up the previously used address.
Then you can sign in to your account then change the email address to the one you would like to use.