If you already own a license, you can access the installer at download.stata.com . You will need the username and password sent to you via email upon purchase.
If you buy a new license today, you will likely receive the latest version rather than version 17. Stata offers different pricing tiers based on your status: Installation guide: Download (Windows) - Stata stata-mp-17-full-version-download
You cannot officially download Stata without a serial number and login credentials provided by StataCorp . If you already own a license, you can
is the fastest version, designed for multicore and multiprocessor computers. If you already own a license
You can request a legal evaluation copy by filling out a form on the Stata Evaluation Page. If approved, they will email you a temporary license key valid for about 30 days.