Downloading Problem. Please help!

I got on the website and clicked the link to download the application and it downloads successfully but the problem i’m having is that i go to click it open and it doesn’t open? please someone help with any suggestions

i am allways having to reformat my computer and this has happened to me before too , i think i downloaded it again but from another website and it worked but it is very slow to open and i cant get it online
, i just thought it was because i have windows 7 64 on an old laptop .hope it helps

The first thing I would recommend is to uninstall Horizon and download the latest version from the link below.
Download Horizon 2.8.0.1