I need to install the software on the new computer, but during registration, I got a message that my Serial number: P2- is already in use. Please, advise.
I have removed the serial number from your post, this is a public user to user forum not Magix Support, please do not post any confidential such as order numbers, serial numbers and contact details in the forum.
The error message you are getting indicates that the software was originally registered to another email address.
If you know the email address and password, you should be able to activate the software, and/or change your email addrss to a new one by logging in to your account on the Magix website and change your email address then activate register the software using the new email address,
If you have forgotten the password, then you need to contact Magix Support by email to infoservice@magix.net.
Note, assuming you are trying to install on a new Windows 11 computer, some features such as hardware acceleration of import/export and some effects may not work correctly. The software you are trying to register is at least 11 years old, and is no longer supported.
You should qualify to the current version, for the upgrade price, now called Video Deluxe if you have Movie Edit Pro.
The downside of this is there have been many changes to the software features such as Harware Acceleration, which will may not be available depending on the graphics card/chipset of the new computer, effects and the Project file format which may not load old projects correctly.