Hello all. I own a PowerBook G4 800 MHz and I tried to load software update today which is usually no big deal. And, like most of you, I found that it's not working today. On top of that though, my computer makes this loud piercing sound whenever I check from System Preferences. I've never heard this sound before and if I quit System Preferences, it stops. I've tried restarting and it does the same thing. Is this normal, and if isn't is there something wrong with my PowerBook? Thanks for your help.