Sven,
Does the unknown device have a device id?
Eg. In device manager, select the unknown device, tab page details, change the property "Device Description" drop down to "Hardware Ids"
What does it say then?
For ex. for an intel PRO 1000 MT network card you get something like:
PCI\VEN_8086&DEV_100F&SUBSYS_075015AD&REV_01 PCI\VEN_8086&DEV_100F&SUBSYS_075015AD PCI\VEN_8086&DEV_100F&CC_020000 PCI\VEN_8086&DEV_100F&CC_0200
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Wil