I will offer several comments.
- Do not use a wireless network or Wi-Fi. Use a wired connection between the two computers. Either an Ethernet cable or preferably a faster USB cable. Using a wireless connection will likely cause data corruption.
- The OS on the old computer need not be updated. The OS is not transferred.
- Your problem may well be Norton 360. Antivirus apps are a waste of your money, and are unnecessary. They WILL seriously slow down your computer and often cause other problems. Use Norton's uninstaller app to remove it completely.
Here are the steps to follow using Migration Assistant. It is very easy to use. Be sure to read and follow its instructions. Basically, the process is as follows.
You first begin by starting the process of setting up your new computer. You will at some point be asked if you wish to transfer files. Respond YES and follow the instructions you will be given.
· You will be told to turn both computers on and activate Migration Assistant in the old computer.
· The computers should be connected with a cable to facilitate the transfer. Wi-Fi is not suited for a transfer of so much data and corruption often results.
· You will be given several options of what to transfer. You will likely want to transfer your settings and preferences.
· You can transfer all or none of your files. You do not have an option to select certain files to transfer. If you wish to do that, then do so manually. You can transfer all or none of your installed apps. Some people elect to download fresh installations to the new computer instead.
· The old computer's operating system will not be transferred. No data from the old computer is erased.
· Allow for up to an hour for the transfer process to complete once you start it.
· Keep in mind that depending on what OS the old computer is running, there may be some 32 bit apps which will not run in the new computer which only runs 64 bit apps.
· It should set up the new computer the same as the old one.
· When that is successful, you can log into the new Mac with the old User Account name and password and delete the brand-new user created during setup or leave it in place as a second admin account.
Enjoy your new Mac.
I hope this is helpful. Good luck.