I have the twian driver from Ricoh - I just have no way of adding the scanner as a device.
You are right about the business to business supply - the scanner/printer was bought 2nd hand from another business that was going bust.
I have tried the 'support' number on the printer - that rang dead, I tried the email address and no reply - no bounce though either. I may yet get this working :-)
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So presumably you need a driver for Windows for the scanner (which you'd expect to be bundled with the pinter driver as this is a multifunction applicance).
Incidentally, I have come up against a similar issue with a film scanner -- resolutely refused to work except via Photoshop Elements.