Is Ghost installed on the hard disk of your machine?
Booting to DOS is not a bios setting, but a boot partition or boot manager setting.
You did not mention what version of Windows you are running, so all I can really suggest is to boot the machine to DOS or WinPE using an external diskette ideally, and then set the windows partition as the active partition using any suitable DOS utility, or WinPE's diskpart utility.
You can run Ghost 2003 from a bootable WinPE disk running WinPE 2 and above, which means you don't need Ghost on the target machine and therefore less risk of stuffing it up.
There are other issues relating to the age of the hardware you are trying to run it on. For example, if your system has SATA disks then PCDOS is highly unlikely to be able to read them, as DOS does not understand SATA and equally does not understand large hard disks. At that point, bios settings for hard disk "compatibility mode" may need to be enabled. However, its much better to use WinPE and add any necessary SATA drivers to it than to risk messing up with DOS.
So the next step for you is to accurately define the version of windows and the hardware in the disk area. Once we know your setup in more detail we are more likely to be able to help you.
There are other limitations that Ghost 2003 will have; it will not understand 4K sectoring on modern large hard disks. Ultimately you should really consider updating to a modern version of a disk management tool. Ghost is still available although more suited to corporate environments, but tools such as Paragon Partition Manager are ideal for one off use, and contain inbuilt functionality to create bootable CD's/DVDs/USB Keys running WinPE and the partition manager toolset. All you need to do is to download the (Free) Windows ADK, and install the Win PE tools to default locations, then install partition manager and point it at the ADK. You can then build your boot media.