While you can certainly work with Odoo under the Windows environment, most of the community agrees that it is better to run your Odoo server under Ubuntu. At the time of publication, the stable release version is 16.04. Here are some resources that can help you get started with Ubuntu.
If you are planning on working with Odoo and Ubuntu you will want to begin by getting familiar with the official Ubuntu website:
Resources for downloading Ubuntu in various formats and configurations can be found at the following URL:
The official Ubuntu website has a comprehensive set of documentation that is a great reference for troubleshooting your Odoo installation: