When you setup AssetAccountant for the first time, a free demonstration fixed asset register is provisioned for you with 10 or so assets for you to get familiar with our system without having to risk any of your own data.
Although you can't remove this register, it is accessible only by a separate button "Demo Register" and does not appear in your active register list (Register Settings).
If you have a register called "Demo" or "Test" in your register list, this may be one that you or your team with access has created.
As with all registers you create, they can be archived at any time by visiting Register Settings > Archive Register.