Depending on how you originally acquired the software, your serial number can typically be found in the following locations:
If you have upgraded in the past, Sound Quest notes that you are "already registered" and may not need to re-enter the number if your account is active. Contact Support: midi quest 11 serial number
Search your email inbox for terms like "Sound Quest," "Midi Quest," "Sales Receipt," or "License." Check your spam folder as well. Often, the serial number is embedded in the original purchase confirmation email. Depending on how you originally acquired the software,