Large Package Glitch/Virus

Hi, when I try to open a large unity package such as Autumnal Nature Pack, or Modern Ruins, I get random programs that pop up which has a bunch of japanese lettering. When this happens, my computer is unresponsive. This is only in large packages, small unity packages work just fine. I scanned my computer with several programs, not a single virus. Any hints or clues on what to do? I don't exactly want to reinstall Windows or do a hard drive wipe.