Once you have the .exe file downloaded, follow this protocol to avoid failed installs.
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The full license for AutoCAD 2015 is no longer sold as a perpetual license. However, the 30-day free trial remains the best way to test compatibility with your existing hardware and workflows. Once you have the
Before you download and install Autocad 2015, make sure your computer meets the minimum system requirements: Autocad 2015 Download Free Trial
If you have an active AutoCAD subscription, you are entitled to "previous version rights." Sign in to manage.autodesk.com.
This is usually a corrupted DirectX or .NET framework. Run Windows Update completely, then install .NET Framework 4.5.2 manually from Microsoft before retrying.