Corrupt downloads, non asus mobo, help pleasE?

Hello, I think this is a software problem since the hardware is working?

Anyways, so anything and everything I download is corrupted, and I've been to dozens upon dozens of websites and each time i download something it comes out corrupted.

I was reading up and it seems like other people had this problem with an asus board + nvida firewall, but I have a dfi lanparty mobo so why am I getting the problem? I also have the nvidia firewall installed, does that just screw up every system?

If anyone could tell me how to fix i would be much obliged, also reformatting really isnt an option, so anything not drastic as a do-able, fix-able, answer would be great.

thanks a lot.