Downloading From Internet Results In Corrupt Windows?

I recently go tthe new comp and then ran into some errors when downloading off the internet, Files turn corrupt most of the time on IE or Firefox and other times it might want to work, Downloading the install for Winamp is one which will corrupt every time no matter how I try it, check for virus's, spyware, turn everything else off, turn off the firewall and I've done all that and still haven't gotten anything. I've been told I should try and update my bios but I know that could only cause more problems in certain cases, Even when trying the asus auto update it says that it couldn't uncompress it. One of the classic errors is" NSIS error, The installer you are trying to use is corrupted or incomplete.

This could be the result of a damaged disk, a failed download or virus. It may be possible to skip this check using /NCRC command line switch(Not recommended )". As well as say if any torrents that I get bit comet says it's corrupt and ones that work in the regular bittorrent downloader go at trash speeds, router I was on was set up before this so it should still be good. I hope this is enough information, if more is needed I'd be happy to tell you. I also cleaned the regestry and checked for viruses and malware as well as anything else I could think of.