If you have any identical models of computer still with the manufacturer's image installed, open Device manager and have a look at the PNP id's of the network card and of the SATA controller.
Then check that the PNP id's are present in the INF files associated with the drivers you are trying to install. The plug and play process identifies the correct drivers by searching all the INF files for a matching PNP ID.
I don't know whether the WinPE implementation in GSS 2.5 offers a 64 bit bootable version of WinPE as well as a 32 bit version. I've assumed that only a 32 bit version is required if you are deploying ghosted images, but if you are using a scripted install based on an image of the operating system install CD or DVD, then a 64 bit O/S install would require a 64 bit version of WinPE.