Here's what I did. Maybe it's too late to help.
1) install the latest vista driver
3) go to device manager
4) right-click on unknown device and click update driver
5) Select Let Me choose and select an imaging device
6) Click have disk and browse to c:\windows\fjmini and select fi4120c.
7) let it install the unsigned driver
8) You may have to restart after installing
9) Try opening your scanning software and then select the WIA driver for your scanner
I've installed 6 4120c scanners on windows 7 systems now. Works perfectly.
Hope this helps!
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