What is wring with my computer?

i keep trying to download thing of the internet but my computer wont allow it i cant download anything i use the downloading website isohunt but even that doesn't work when i download it the box comes up and when it is finished it stats verithing it and then when i click run it Just goes help me i know i have posted a similar question before but the answers were no use i have checked my firewall and hav done that thing were you click on tools and then Internet options on the internet but even that dosen'tt work i cant changemy bbrowserse it wont download plese help me someone