I installed the Western Digital 250GB hard drive in my zt3000 and never got it to work properly. I kept getting corrupted system files such that it wouldn't boot after shutting down. I tried several disks with the same results. At first I thought it might have been software related (it still may be), but when I restored my smaller drive, everything went back to normal. This tends to support the hardware being the problem, not the software.
If anyone has any ideas, I'm certainly open to them given that I wasted days on this problem.