Inaccessible_boot_device happens when the OS can not boot because it can not find the adecuate driver.
It happened to me when I Upgrade my computer and used the same driver.
As I had my old PC this is what I did.
Insert The cd drivers of my new computer.
Went to Control Panel Click on System Icon Click on Device manager Click on Hard Disk Controller Right Click on IDE Controller Right Click on Properties Click on Driver Click on Update Driver Went to my Cd and find the ide controller driver Once updated the pc shows a message telling that the driver it is not adecuated for the system Click on OK. The system will reboot. Turn off the Pc.
Install the disk in my new computer.
Turn on my New Pc.
My dear Bill it is so easy. Where is the Documentation?