It's possible that you may have made a change on purpose that resulted in that black arrow displaying or there may actually be a problem.
No matter how the black arrow showed up in Device Manager, there's usually a really easy solution.
If you see a black arrow, it doesn't necessarily mean there's a problem with the hardware. The black arrow just means that Windows 7 or Windows Vista is not allowing the hardware to be used and that it has not allocated any system resources to be used by the hardware.
If you've disabled the hardware manually, this is why the black arrow is displaying for you.
To remove the black arrow from a particular piece of hardware, you'll need to enable the device in Device Manager. If there is truly an issue with the hardware, the black arrow will probably be replaced with a yellow exclamation point after enabling the device.