Hitachi HF-W6500 Instruction Manual page 277

9. TROUBLE SHOOTING
(21) "?" or "!" is displayed by a device manager.
<Possible cause>
Device Driver is not installed.
<Action>
1. When a device is "A", please refer to section 4.8 "Display of Device Manager".
2. When you implement an expansion board, please install a device driver.
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