I have an old z1 sitting around the house in which the harddrive went out. One of my buddies z2 screen got cracked by accident i swithced the HDDs in them and my unit would not read his hdd is there something i am missing? it should be plug and play correct?

It will not plug and play. The drive was locked by your Z, and only your Z will read it. The drive can be unlocked. Check the sticky posts in the Z series hacks forum, and my ads in the classified section.