There can be several reasons why you may be encountering an error when installing Odoo 15 on your local computer. Here are a few potential issues and solutions to check:

1. Requirements: Make sure that your computer meets the minimum requirements for running Odoo 15. This includes having a compatible version of Python (3.6 or higher) and PostgreSQL (9.5 or higher) installed.

2. Permissions: Make sure that you have the necessary permissions to install software on your computer. If you are installing on a Windows machine, make sure that you are running the installation as an administrator.

3. Downloaded package: Make sure that you have downloaded the correct package for your operating system and that it is not corrupted. You can try downloading the package again and running the installation.

4. Firewall: Make sure that your firewall is not blocking the installation process. You can try disabling your firewall temporarily during the installation.

5. Duplicate installation: Make sure that you do not have another version of Odoo already installed on your computer. If you do, it may be conflicting with the new installation.

6. Error messages: Carefully review any error messages that are displayed during the installation process. They may provide useful information about the cause of the error.

7. Ask for help: If you continue to experience issues with the installation, you can seek help from the Odoo community or a professional consultant.

It's also worth noting that it's a good idea to check the official documentation before installing, this can help you to be aware of any particular steps or requirements that you need to follow.