I just installed a new Seagate 7200 RPM, 8-Mbyte buffer, 200 GB Hard Drive in this G4-AGP. I realized the G4 would only see the 200 GB as a 128 GB drive and that is not an issue as I only need about 25 GB. I now have the Seagate 128 set up as my primary drive (the Master) and my old WD 40 GB as the secondary or backup (slave) and I back up using Carbon Copy Cloner. I have lots of room for additional storage. I understand there is a software product that will let users access the unrecognized portion of the 200 GB drive but I do not need the room at this time. No problems at all and the drive works great! Dick http://www.seagate.com/support/disc/manuals/ata/cuda7200pm.pdf