This article applies to OS X Yosemite 10.10 through 10.10.2 only.
If your Mac stops responding and shows a spinning wheel after you create a user account in Setup Assistant, allow setup to continue. The setup process will resume after about 30 minutes.
If you restart your Mac during setup, Setup Assistant will appear again. If you continue setup and see a message that the user account you're trying to create already exists, create a temporary user account to finish setup.
You can avoid this delay if you complete Setup Assistant without connecting to the Internet. When Setup Assistant prompts you to select your Wi-Fi network, click Continue without selecting a network. If you have an Ethernet adapter, disconnect it before you start the setup process. After you complete Setup Assistant, restart your Mac. You can then join your Wi-Fi network or connect your Ethernet adapter.