I just bought a Hitachi USB 2.0 XL1000 external hard drive. The first time I plugged it in, it showed up and opened with time machine. But then Time Machine suddenly quit, so I unplugged the drive and now it won't show up when I connect it-the drive makes the sound that it is working, but then after a while it just turns off again. I am new to this, any help would be greatly appreciated.
are you connecting the drive to your Mac directly or via a USB hub ? have you tried a different USB port and/or cable ? is the drive showing up in system profiler ?
additional troubleshooting steps can be found in this support article: USB and FireWire Quick Assist. also here: If a USB device isnt working