As mentioned above, version 7.5 is a very old release, and also, booting to PCDOS limits you to IDE/ATA hardware, or SATA only in compatibility mode. Do you have smartdrive loaded in DOS? This can speed up disk transfers, but you may need to play around with other drivers (for example remove mouse driver) if you find there is insufficient free RAM for Ghost to run when smartdrive is loaded.
You should also consider testing WinPE as the boot system instead of PCDOS as this has native support for modern hardware such as SATA hard disks. You can also add new drivers as required.
The article at:
https://www-secure.symantec.com/connect/articles/readyadventures-winpe
will get you started with a WinPE on a variety of boot media. Since WinPE also supports USB connected hard disks, you could backup and restore to a local HD rather than the network, which can also prove faster.
I have certainly had no problems using Ghost 8 with WinPE to backup hard disks, so you may find that 7.5 is also useable in this way.
If not, you could also check out imagex.exe which comes with WinPE as this can create images as well, and since imagex does not include swap files in images, they can be smaller that the equivalent ghost image.