I built a new PC and would like to move Movie Edit Pro to the new PC. When trying start a new project it mentions deactivating the software on my old computer, but I can't find how to do that.
Welcome to the Magix user to user forums.
If you still have access to your old computer, simply open MEP on it, go to Help>Deactivate program.
If you cannot open the program on your old computer, go to your Magix account, log in, go to My products, find the listing for the relevant version of MEP. Below the serial key should be a "More details" link. Click it and you will see ALL the registered activations for your version of MEP; simply deactivate any and all that are no longer needed.
HTH
Jeff
Forum Moderator