unknown device.???

ive recently had something strange happen.in my device manager i have something called unknown device with a yellow exclamation mark beside it.could anybody explain what this is please.?
ive looked at the properties of this and it says its an unknown device and there are no vendor details at all.
ive tried troubleshooting this and windows cannot find any drivers for this,there is no details for it whatsoever.now prior to this appearing my machine did crash on logging off for some bizarre reason.im puzzled as i cant identify what the device is.i finally decided to uninstall it with no problems so far.
any ideas on what was happening please.?

many thanks. ???