Try this. Open up task manager (Ctrl+Alt+Del) and go to the processes tab. Once there, right click on any process that wasn't started by windows or a service, and click on "Set Affinity..." If that option is greyed out, or the box that opens up only allows you to select Core 0, then there is something wrong and you should back-up and reformat. However, if it allows you to select Core 0 and Core 1 then there is just some error in CPU-Z. (That software is often not correct on a few different things).
The fact that it's listed in the Device List twice tells me that it's more then likely working properly.