Yes, you can register the new server before disabling the first one.
Please download the installer from your account at https://clients.translation3000.com to make sure you have the latest build of your Projetex.
I recommend making a backup of the database on your old machine and restoring it on the new one.
Also, you will likely need to copypaste the contents of the "BusinessServer" folder to the new machine as well.
If you receive a "database requires an update" error after restoring it on the new machine, please run the installer again. Ir will automatically update the database.
Once the new server is ready, you will need to link all workstations to it: Restart them, click the Server button in the login dialog, and enter the address of the new server in the corresponding field.