I recently got a macbook pro to use for photography and I bought Parallels to go with it so that I could put my PC Photoshop on my Mac. I have the Parallels set up on my Mac but cannot figure out how to get it to run my programs. It says I need to install windows itself before I can continue. Is there a way to connect my old PC's windows to this mac? Or do I have to buy windows and put it on my mac?