I have a PowerBook G4 titanium with 800Mhz and 512mbs of ram, and my computer has recently been crashing. It starts to click, and the little swirly thing appears, then totally freezes and i have to force shutdown by holding the power button. Is my harddrive dying? i'm currently backing it up onto a 500gb external harddrive... would i be able to boot from this and use it if my harddrive totally dies? what about ram?? thanks!