I'm not up to speed with all the options available with GSS 2.5, but what I would be aiming for, to avoid any risk to your existing system, is to install GSS2.5 on another system and see if it is possible to create a bootable CD or DVD that includes any drivers required by the hard disk controllers on your server.
Ideally, your server could then be booted from the optical media, and the relevant drive imaged to a USB connected hard disk (or other installed drive).
The Articles tab on Connect can be searched for an article titled "Adventures in WinPE" as this details a procedure for creating bootable WinPE media and installing additional drivers and how to use ImageX to create images (similar to Ghost but free).
GSS2.5 also uses WinPE to create its boot systems so the techniques are similar, albeit GSS makes it slightly easier to install additional drivers.