When the computer starts and the first screen appears, try and pause it with the erm " pause " key on the keyboard.
Does it show details for
primary master drive
primary slave drive
secondary master drive
secondary slave drive.
If it does, what are the settings for the above.
If this screen does not show. Enter the bios, usually by tapping the delete button as the computer starts. look in the first page, usually standard cmos settings. Are the above settings shown there?