This is a common problem for some firewalls and virus scanners when downloading files from the internet. The firewall/scanner makes a small change to the downloaded file and Windows erroneously reports that the file is corrupted. 

Solution:
Temporarily turn off your virus scanner and firewall when downloading the trial. Don't forget to turn it on again afterwards!

If you still receive this message after taking the above steps, or if you are uncomfortable about disabling your firewall/virus scanner, please contact us and we will send you a link to an alternative version of the installation file which will not be affected by your firewall/virus scanner.