I am having some problems trying to accomplish this. I had to disconnect my HD with windows on it to install ubuntu on a separate HD. I installed it on an external usb HD. It worked fine, and ubuntu boots right up. Problem is, that when I connect my HD with windows on it, now matter which HD I boot from, windows starts right up. And even when I disable my windows HD in bios, and then boot from my ubuntu HD, I get an error and it wont work. So ubuntu will only boot when my windows drive is physically disconnected. I'm guessing this must be caused by my motherboard's controllers or something like that. I'm thinking about buying a new SATA 3 HD, to install ubuntu on instead of the mybook USB HD I'm using now. I'm not sure though, if it will work, or if I'll be in the same boat I am with the external. Anyone accomplished this? I have an asus sabertooth p67 motherboard.