I just thought I'd mention this for anyone who is thinking of using a Western Digital 1TB drive on your PPC Mac running 10.4. Short story: the MyBook Essential 1 TB external USB 2.0 drive is not compatible* out of the box with my Mac PPC G5 computer. If I plug it in, I get a message that the drive is not readable and an offer to initialize it. However when trying to partition the drive using Apple's Disk Utility (in 10.4), I get formatting error: Input/output error. The solution is to download the WD Macintosh + Turbo Drive utility from Western Digital and install it on your PPC Mac. As previously mentioned, I have a G5, so while I assume this should work for any PPC Mac running 10.4.11, I don't know for sure. * If you have an intel Mac there should be no issues with this drive requiring the utility to be installed. This hard drive worked as it should when it was first plugged into the MBP. see my post below.