Can't download/can't run downloads

Hey,
Recently i updated my computer from Windows XP to Windows Vista. I had Windows XP crash on me, so I went ahead and just reinstalled my laptop but with Vista this time. It took two attempts, the first time, it crashed while installing. The second time, everything went very smoothly. I've just logged on and I downloaded Avast and I tried to download Firefox, but it won't run Firefox. No biggie i suppose, then I downloaded Frostwire, during the installation, it tired to install the latest Java update and an error notification came up saying that it couldn't be installed. It finished installing and now Frostwire won't work. I tried to download AIM also, and it refused to download it. I don't know what could be wrong, though if anyone could help, that would be amazing. Thanks, Hoboken