Resend your licence key
Lost your key? Enter the email address you bought with and it will be sent again. The key goes to that address only. It is never shown on this page, so nobody can read your key by typing your address.
Asking uses nothing up. The key is rebuilt from the payment record each time it is sent.
Why it is emailed rather than shown
If this page showed the key to whoever typed an address, anyone could type a colleague's address and read their key. Sending it to the buyer's own address costs you a minute and makes that pointless.
You may not need it at all
Reinstalling Windows or moving to a new machine uses nothing up. There are no activations to run out of.
If your old machine still has %APPDATA%\Heimdall3D\licence.key, copy that one
file across. That is the whole move.