I cloned my SSD onto a new computer, and DT is working fine. But should I deactivate the previous DT installation in the old computer? The old machine is going to be formatted and sold to someone.

Hi. I would strongly recommend a secure wipe of your drive to remove everything before selling it. Easy to do, protects you, and gives the next person a clean slate.

As far as DT is concerned, I think you are only supposed to have one person per license anyhow, so that is another reason to delete the app and all associated files from your drive.

I agree with Frobgoblin on this. If you’re selling it, I would take the time to do a secure wipe.