Is it possible to download rosetta on windows 8? The reason why I am asking is because I downloaded rosetta 3.5 and got a gz file that wouldnt open.
Regular Rosetta doesn't officially support Windows. It's built around a unix-like command environment, so Mac and Linux work well, but you have to use things like cygwin to get it to work on Windows, and that gets messy quick. (There's ways of using both Windows and Linux on the same machine that I might recommend instead, if you can't get access to a dedicated Linux or Mac machine)
PyRosetta, on the other hand, should have a Windows release. The "drawback" is that you'll be using a Python scripting environment rather than commandline programs, so it will take a bit of learning to transition a commandline Rosetta protocol to a PyRosetta one.
Rosetta won't work without major modifications on a Windows PC, but you can install it on a Linux virtual machine and then use it to run Rosetta. That's what I am doing, for simple things I works perfectly fine, for more complex problems even a state of the art PC is simply too slow (unless you have plenty of patience).