I've just created a new steam account and wanted to activate Half-Live there. Then I got this error message:
When I click on 'Retrieve Account', nothing happens. I am quite sure that I have already activated this many years ago on another account, but I don't remember which account (and which email-address) I used.
When I click on 'See the Steam support site for more information' it seems not to contain helpful information.
I have the original CD and even the receipt.
What can I do now?