GIMP and Silverfast on Windows

Hello there, dear readers!

Currently I am trying to revive an old but still working scanner
(Microtek Scanmaker III). In a way you could say it came with Silverfast
which I updated until Version 6.0. Unfortunately the original I ordered
was a Photoshop plugin so I am kind of stuck with that now. I have no
Photoshop license for this computer, so using that isn't an option.
Besides, I am trying to use OSS where ever I can.

Currently this Computer is only running Windows XP SP2. There is an
installation of FreeBSD planned (and SANE with it) but sofar I haven't
gotten round to that. So for now, we are talking GIMP für Win32 here.

There is no scanner driver other than this plugin at the moment. I have
a very old version which also came with a TWAIN module but this was
written for 95/98 and doesn't even recognize my SCSI-card (Adaptec
2940 U2W).

I went and downloaded PSPI[1] for the job and installed it. But somehow
I can't get the GIMP to play nice with Silverfast. There are errors of
certain files missing, so now I am guessing that this version of
Silverfast is not really stand-alone but instead needs certain files
from Photoshop to run.

Is it at all possible to get these two programs to work together?