Are you booting to DOS or WinPE?
Chances are high that you lack the correct drivers for your SATA chipset if running WinPE, or if running DOS, you will be unable to access a SATA device as DOS has no SATA support. Therefore, if your bios offers a hard disk compatibility mode to emulate the older PATA standard, try this and see if you can then see the hard disk.
If none of these help, then please provide details of the exact build version of GSS 2.5 that you are running, and the hardware and operating system you are trying to image. If it is Win 7, you need 2.5.1.2266 at least.