Just replaced a nonworking HD in a Macbook. Seagate, just like the old one, plugged in & found it & partitioned in Disk Utility, however, after naming the HD, when I go back to reinsall the OS from the original disks, I get an alert "This software cannot be installed on this computer" and the options to either Restart (which gets you back to the same place) or Startup Disk, which gives you the option to choose the OS install disk to restart or a Network Startup (with a question mark on it). The newly installed HD does not show up here, altho it can be seen in disk utility. Any thoughts?