The Makefile would, in oder to work properly, like to have a file autoconf.h. An appropriate File can be obtained via copying the file /boot/vmlinuz.autoconf.h to /usr/include/linux/autoconf.h. E.g. using a virtual console, you could do this as follows: (Be root again, just to be sure.)
Welcome to SuSE Linux 7.2 (i386) - Kernel 2.4.9 (tty2). athlonlinux login: root Password: You have new mail in /var/mail/root. Last login: Thu Oct 4 20:04:02 on tty1 Have a lot of fun... athlonlinux:~ # cp /boot/vmlinuz.autoconf.h /usr/src/linux/autoconf.h athlonlinux:~ #This should be perfectly correct for the SuSE 7.2 distribution. For other distributions oder later versions of the SuSE, you probably have to search yourself for something called autoconf.h. This can be done e.g. via
locate autoconf.hwhich should list all files of interest at this moment. (Probably you have to execute updatedb fist and wait for it to finish, if you have just installed the kernel sources for the first time before). Just to be sure, you could also compare the error message of make (the one where grep complains...) in the plustek_driver directory again with the one mentioned above, because this might also be subject to change. But after that, the error message with grep not finding autoconf.h should no longer appear when trying to make.