I looked into this and here's what I found out:
"Upon purchase, an email is sent to you containing your license information. The email is sent to the email address inputted at the time of purchase. Please retain this email for future reference."
OK, great - if you've still got the email. But if you haven't, here's the bit of info you'll need:
Don't forget to give support as much information as you can. Your full name, address. NOT your credit card number that you bought the software with though. You should NEVER send that out over email. But if you can include your email address - the one you used when purchasing Regnow, that'll go a long way to helping them find your purchase on the system.
Good luck and I hope this helps.