I would like to thank everyone that makes this upgrade possible. I did the Z1 to Z2 upgrade earlier this year. I just completed the Z2 to Z3 upgrade while preserving my phone book and keeping my music. Everything went well and is working fine thanks to the great instructions on the site. FYI, I kept my original Z1 hard drive and used a new one for both upgrades. I used a Hitachi hard drive, model DK23FB60. I have been using this drive for the last 6 months with no problems (rebooting, freezing, etc.) I would recommend this drive if you cannot locate a Toshiba drive.