Mine used to beep when I would try to wake it up, it would spin down when idle. The computer wouldn't sleep though, just the drive, and when I tried to wake it up, it would beep over and over like it couldn't spin up or something. Then finally it would spin up, mean while on my Mac, I could use it, but every time something needed to use tha hard drive, that app would just beach ball out. So since the whole computer never sleeps anyway, I just made it so the hard drive never goes to sleep now, no more beeping, it was freeking me out for a while though, it the original drive from a dual 533 that I bought new.