I have a Mac Pro 2.1 2x 3ghz quad-core intel Xeon processor, 32GB 667mhz ddr2 FB-DIMM ram. Running 10.7.5 (lion) I've created a SFOTT drive on various different USB sticks and internal drives with different versions of Yosemite. Originally it would boot to a black screen with the apple logo and white writing (kernel panic) before restarting. After trying a different yosemite app (which I bought already on a USB stick from eBay) nothing happens. I'll select the SFOTT disk on startup, I'll get the apple logo and the spinning wheel and then it just boots to my lion install. I've tried plugging into the back, plugging into the front, using an extension cable etc and switching between the original graphics card and my new Radeon HD5770 1gb. Have I missed something? Everyone else seems to find this easy, but I have had nothing but trouble!