Ghost Solution Suite

I'm trying to save a HDD image backup to an external USB drive, using Ghost 11.5 in DOS mode (like using the old PC-DOS floppy diskette); but my CD does not recognize the external drive. My experience has convinced me that the safest way to protect my system is to clone from DOS. Is there a way to create a boot disk with v11.5 with USB drivers, so that I can clone and restore my HDD from a USB drive with a boot CD?

when you create your boot disk try using the override BIOS USB control option if the default settings dont work on your machine. 

I would recommend however that you use the 32bit PE based boot disk if you want to image using USB.  it has much better support for USB and tansfers at much higher speeds than dos mode does.  I have used both methods and find PE works better for USB, though i use DOS for network based imaging.

DOS is increasingly outmoded for hard disk imaging due to the evolution of new and different hardware. PCDos does not support SATA and there are increasingly more complex chipsets finding their way into new machines which do RAID on SATA, making it necessary to add drivers to the boot system which can support these chipsets. WinPE can do all this whereas DOS cannot, as manufacturers are just not writing drivers for DOS anymore.
WinPE can also make USB devices bootable, so you can not only boot off your USB device, but you can backup to it.

Do not forget to update to 11.5.0.2141 (at least):

http://service1.symantec.com/support/on-technology.nsf/854fa02b4f5013678825731a007d06af/b9d1a099585a4ad7872574d60054cd1a?OpenDocument