You may want to try installing xsane in Synaptic.

Go to the makers web site with your scanner version numbers and in the
Support section see if they have Linux drivers for it. Download and
install those if they exist.

First go here, http://www.sane-project.org/ and see if your scanner is
supported

(http://www.sane-project.org/sane-mfgs.html#Z-MICROTEK)

If it is supported you can acces your scanner through Sane (you might have to
install it though synaptic)

If it isn't supported (and I don't see a i800 in there) you need to check the
manufacurers site for modules.