I use a GT 7000 scanner (USB) and found the same difficulties with support for newer versions of Windows. In the end, what works for me is to boot Ubuntu Linux and somehow GIMP picks up the scanner as a source. I guess that someone must have made that homegrown solution and put it somewhere in Linux.
A slight correction: it is Xsane that picks up the scanner without any configuration, not GIMP. I used ubuntu Edgy live CD, which is also quite old.