If you have lost the serial number you were issued after purchasing Cart32 you can always have us resend it to you. Just email us or submit a ticket with the exact company name you registered with and we can look up the serial number for you.
If you're not sure of the exact company name, you can find it by going to your shopping cart, leaving off everything after Cart32.exe in the URL, and checking the line that says "Registered to <Company Name>" in the new page that opens. Here is an example:
In the above example you'll notice the cart is licensed to "MWA Inc."