Having a Voip-conference later in the day, I searched through my older hardware I still had lying around and dug up my Sennheiser headset.
It didn’t came with any drivers, so just plugging it into the USB port should be enough.
No such luck :S
I got a Windows driver error: This device cannot start. (Code 10). After a bit of googling it appeared that the device was not compatible with Windows Vista and Windows 7.
Not giving up, I finally found a firmware upgrade for the PC35 USB headset itself. Although there is no information about it, the update is only compatible with 32bit versions of Windows.
Firing up my trusty Acer One, I upgraded the Sennheiser, plugged it back into my Windows 7 64bit and now it works like a charm.