I have reformatted the entire hard drive using fdisk, created a single partition (hda1), and run mkfs and fsck successfully. Attempting to boot the computer now results in a GRUB error.
When you did that, you removed ALL operating systems. The first stage of grub is still in the MBR (the boot sector of the hard drive), but the rest of grub no longer exists. So, boot hangs and you get error 15.
From Solving Boot Problems with Grub - 2nd Edition:
Grub Error 15 : File not found
This error is returned if the specified file name cannot be found,
but everything else (like the disk/partition info) is OK.
Grub is telling you that the partition is OK, but it can't find the specified file (the next stage of grub) to continue booting.
Since the CDs from the book don't boot, but your DSL livecd does boot, you can only conclude that the CDs from the book are defective is some way: either scratched, or boot script not working, something is not working as it should. Either that or they are not intended to boot. Perhaps you are supposed to copy the iso from the cd, then burn it to cd. Even if it isn't supposed to work that way, you should be able to copy the cd to disk, then make an iso to burn to disk, keeping in mid the issue of md5sums (see the last paragraph).
Running fdisk /MBR is pointless since you don't have windows installed now that you have formatted the drive.
To install Debian you need a disk that boots from the cd drive. If the disk from the book doesn't work, I's suggest that you install DSL (sincd the partition is formatted for Linux). Then download the Debian iso and burn it to cd (don't forget to compare the md5sum of the downloaded iso with the md5sum at the site you download from). Then use that to install Debian. The same applies to any other distro you choose to try.