Hi, once someone said you can easily use in and put 3TB HDDs into PowerMacs, as long as you format as GUID (which is the partition scheme for Intel Macs, so you will be able to write all data to it, but won't be able to start the OS from it, which is not a purpose for that big of a Drive, my opinion). In other Forums I read, that only 2,2TB will be recognized. If you are in a hurry jump to Conclusion! What did I do? Put the 3TB Drive in my G4. started with 10.4. 3TB were recognized in disc utility. I do not know, but I guess I then formatted it under 10.5 with GUID to one 3TB partition. I then strated 10.4 again and wrote data to it. After I had filled it and 900GB were left, I got a kernel panic, which resulted in my Boot-Drive being unsusable from then after repair trys. Well, the drive had allready 26 dead sectors, so this might be coincidense. The Pending bad sectors increased from 0 to 50 to 70 and then I stopped using it. I put in another drive with 10.4.11. When I the drive had just about less than 800GB free space, copiing data always stopped (error -36). I then booted into 10.5 and tried to copy the data, that worked fine. Then started into 10.4 again. All data is DV-movies from iMovie. Before, I was able to play these, now no file be it at the beginning of the drive or not could be played, I got the iMovie window with the thumbs, but the play button did not work. Went back to 10.5, every file was playable! CONCLUSION: Under 10.4.11 PPC - 3TB can only be used up to about 1,9TB space (Like other Forum's said: 2,2TB barrier). - data will only be readable, if you stay there and do not add data beyond that under 10.5. As long as you stay in the 2TB range, everything seems ok under 10.4 Under 10.5.8 PPC: - full 3TB is usable - no problems so far. When I have filled up all the 3TB to the end, I will reformat it into two partitions and try, if that works for 10.4 to write to the part beyond the 3TB. So far, 3TB und 10.4 no, under 10.5 yes.