I purchased movie edit pro 14 second hand, and unfortnately the serial number was on the box and it has being thrown out.
Hi
There is very little you can do about this because the product is registered in their name.
Assuming you mean MEP 14 released in 2008, not MEP 2014, then depending on your Windows version you may have problems with the program - up to Windows 7 there should be no issues, however With Windows 8 and 10 it is likely to have some problems and also is out of support with Magix
A long shot - though you are reliant on the goodwill of the seller and that they registered the software and still have their Magix account - is to contact them and ask them to retrieve the serial number from the their account on the Magix website and give the number to you, they will also have to tell Magix they have sold the software to get it de-registered so you can register it.
HTH
John EB