After attempts to load XP on my original 320 HD failed... Every time I start up my computer from shutdown, I get the black screen asking if I want to boot from a CD. I have to hard shutdown and restart with the option key pressed. It, then, shows the main hard drive that has my OS on it. I click on it and all is well. This does not happen if I just restart. What do I need to do to get my Pro to boot from my main HD?