Thank you very much for your quick response. I will try to find the card you mentioned.
But first I will try one of the two PCI-SCSI cards that I already own, a Tekram DC-310/310U and an Adaptec 2904 (both of them with a 50-pin external connection). The problem is that I do not know the type of cable that I need. The card-side-end is clear, but the other end of the cable isn't, because I don't have the scanner in front of me.
When I have the cable, I will try installing the scanner (with XP or 7, I don't know yet), and then I will follow the steps described in the post you send (thank you for the link). But I'm not so far yet...