I am building a computer and for the harddrive I want to put in a 80gb SSD for the operating system and a 2-3tb Hybrid for everything else. Now currently I have a regular windows tower. I am wondering If I can buy the SSD put it in the windows tower I currently own and then download the operating system off of the windows homepage and put it on my current computer and install it on the ssd from there or do I have to buy the disk to install it on the ssd?