Why after removing the third setup disk from my computer and rebooting, does a blue screen saying "STOP 0x0000007b Inaccessible Boot Device" or "0x4,0,0,0" appear and the Setup locks?

Why after removing the third setup disk from my computer and rebooting, does a blue screen saying "STOP 0x0000007b Inaccessible Boot Device" or "0x4,0,0,0" appear and the Setup locks?

There are many causes for these Error Messages. Reference Microsoft Article ID Q122926 for troubleshooting information.