I know it sounds like a weird problem, but here's how it went. My computer started acting up lastly and after a few hours of struggle and lag, I decided to restore it to default. After the restore, everything looked fine, but now that I want to install stuff, I keep getting error messages. I tried google Chrome at first, download failed, same with firefox and opera. After that I tried to download either league of legends and java, both give me the error message (comp is in French, sorry if that translation isn't 100% accurate) : C:\Users\...\Downloads\LeagueofLegends_NA_Installer_9_15_2014.exe isn't a Win32 valid application. and it does the same thing with Java.
The weird thing is, that I seem to download the installers/setup files just fine, but problems seem to occur when I try to open them, I also tried to just execute them rather than save as.. but it's the same result. I downloaded Avira just fine, I also got the Pro version of it. Nothing else has been downloaded yet. I know I'm not that accurate, but I have no clue what's going on so if any details is missing, ask freely. Thanks a lot!