Apparently, if you create a Google Checkout account while creating your Google Android Market account, the Checkout account created is not a full-featured account, it is missing some sections.
Most notably, it is missing the "integration" section where you can get an API key to retrieve data automatically (needed, for example, for integration your own order processing system with Google Checkout).
My question is: is it possible to "upgrade" this "Android Market" Checkout account to a "normal" Checkout account, and if yes, how?