This is normally a symptom of running the installer through the .zip file, but can also be due to interference from 3rd party software.
Please make sure to extract the installer, then close any background software such as your antivirus and Dropbox before running the extracted file.
You may still be asked to restart your computer - please restart.
Once your computer has restarted, the installer should automatically start. It may be necessary to restart several more times before installation is successfully completed.
If you are still having issues, please contact the support team via Live Chat on our website.