Scenario:

* I have a Google Account (not GMail) registered as foo@myisp.com.
* I want to change to GMail as my email provider, dropping foo@myisp.com.
* I don't want to create a new Google Account, as I would have to start over on YouTube, Google Reader, Google Code, Google Docs, etc.


What's happened:

- Create a Google Account as foo@myisp.com
- Create a GMail Account as foo@gmail.com, attached to the Google Account
- Send an email from GMail:
* GMail will arrive with unwanted "From:" of foo@myisp.com - no mention of foo@gmail.com
- Add foo@gmail.com as an alternate Sender on the gmail.com account and send mail
* GMail will arrive "From:" foo@gmail.com, but unwanted "Sender:" of foo@myisp.com

I can't find a way to nuke the unwanted foo@myisp.com completely. This will result in some people responding to the wrong address, which may belong to someone else in the future.


Some things I have tried:

* The non-GMail address can't be removed from the alternate sender settings
* Removing foo@myisp.com from the Google Account and only leaving foo@gmail.com still leaves foo@myisp.com in place in GMail.
* On deleting GMail from the account, I can't set the GMail account as the account address in advance of re-creating the GMail account.


I'm after a solution that works completely within GMail, and doesn't rely on my configuring any extra servers - ie, no sending GMail through a third-party smtp server.