I am talking about Computer OS Microsoft Windows, I am assume you are using old and out of date XP, Win7, Win8 ? did you try " Linux " OS? also the price of hard drive and internet speed is been dropping for some time, also did you update you compression software? is quite be a issue!
The message is from MS Windows.
I just try to download some files.
No issue on just " mp4 " files, only on " rar " file, the massage is coming from >>Windows<<,
I use Windows 10 64 bit, I only use Chrome and FireFox, both is been update it.
Do your site use any Huawei equipment ?