I've created a .dmg to an external drive (formatted Mac OS journaled) and then partitioned 10gb's and dropped the Snow Leopard OSX onto it. I power down, power on and hold ALT. It gives me the option of my HD or the external Snow Leopard partition but when I select it, I get a "you need to restart your computer. Hold down the power button until it turns off then push the power button again" (or something close to that). any ideas as to what I'm doing wrong? 2010 Macbook 2.4 Core 2 Duo with 2 GB ram.