I paste a 'standard reply' from our support ticket system:
To retrieve lost registration information, to download the latest stable SQLyog ENTERPRISE and to purchase upgrades you should use our Customer Portal.
You can see everything that we have registered about you and maintain your data (such as email adress) yourself.
The Customer Portal is available from
http://webyog.com/CustomerArea/
we have you registered with the email adress '******@*****'. You must use this adress too as the userid for the first logon to the system. First you must request a password. It will be sent to you. In case the above email adress is no longer available to you, we will need to change it manually for you to get started with the Portal. If so please tell here what the new email adress should be.
Note that download links and display of registration data are only active for users who still have free upgrades.
For details please refer to our upgrade policy at:
http://webyog.com/faq/30_129_en.html