This isn't really to bump an old thread or anything but after extensive research into the topic (and I mean extensive, I've been searching non-stop for solutions) I have found the problem... And I'm a little embarrassed to tell people my solution as it was so incredibly overlooked but I'm doing it for the sake of search engines! Because I hate when I'm researching a topic and someone comes along and says "I fixed the problem!" and then never says what they did to fix the problem. So, here it is... Windows-friggin'-Firewall. Now I assumed that this wasn't the problem as I tried to disable Windows Firewall before and it didn't seem to fix the problem but then I had a brilliant idea. I decided to disable Windows Firewall BEFORE I downloaded the file. Guess what? It worked! So, I've narrowed the problem down to Windows Firewall! As far as what Windows Firewall is doing behind the scenes that's causing my larger downloads to become corrupt? I haven't exactly figured that out yet. It can't be blocking 7zip, winrar, etc because smaller downloads work for me still AND the solution came to me only when I disabled it before downloading the file... If I figure out the fix I'll let you know but for now all I can recommend is try all the steps I listed in the original post if this doesn't work for you but try disabling your firewall before you download. If that doesn't work and your confident that the file isn't a virus (in this case, I am) disable your antivirus. And if that fails then move onto the steps i listed that i took in my original post.