I have a custom built desktop pc with no cd/dvd drive. I wanted to install 64 bit on it (im currently running 32.) so i made a flash/pen drive with windows 7 ultimate x64 iso. Installed on it. I converted it using rufus, and restarted my computer but it never gave me the option to run from pen/flash drive. I then restarted again and held down f12 to select boot. I clicked on usb. (All of them) and it ran the same thing it always does. I am completely and utterly confused and have no idea what to do. Please help.