Transfer PE7 to another computer

have a Packard Bell computer which has pre installed PE7.  I have bought a new computer and wish to re-install PE7.    It was my understanding that I needed to download PE7 from adobe and obtain serial number from old computer. I obtained software from Belarc and used this to obtain the serial number. I downloaded PE7  and find that when I enter the serial number PE7 will not accept it.  There is a message which says use number for download purchases only.  My number is for pre-loads only so how do I get a number that works?