![disk utility won disk utility won](https://linuxhandbook.com/content/images/2021/08/linux-handbook-cover.png)
If you're following the technique I've outlined, it's wise to try booting from the new external SSD before installing it internally, just to make sure the computer recognizes the drive as bootable. That way, once you restart the reassembled computer, you can at least be sure that there's a drive with a bootable operating system available. Set the Format type to Mac OS Extended (Journaled. Click on the Erase tab in Disk Utilitys main window. When Disk Utility loads select the drive (usually, the out-dented entry) from the side list.
![disk utility won disk utility won](https://i.stack.imgur.com/2NxIN.jpg)
Gives the same result (even if trying GPT mode) : (says near : impossible to satisfy the demand because of an I/O error on the device) It sees the disk, but with a wrong size, and don't accept to format it : I tried using the Windows 7 hard disk manager. The problem is that I cannot achieve to reformat them to use them individualy as standard single drives. The disks do not appear in the W7 "My Computer". I'm on W7 64 bits, on a Gigabyte EP45-DS5 motherboard, on the intel sata ports, AHCI activated, no RAID installed (and don't want to do it). These disk have been given to me and were used on another computer.
![disk utility won disk utility won](https://www.ubackup.com/backup-restore/images/initialize-disk-without-losing-data-3889/initialize-disk.png)
I have 2 internal Seagate SATA hard disks that were, at evidence as far as I can judge, mounted in a RAID configuration.