Problem installing Arduino Uno!

Hundkoja:
My unit is recognized as "Unknown object" in the Device manager. I have tried both Windows 7 and on another computer with Windows XP.
No driver seems to be installed. I am lost!!

Same problem here....unknown USB device. When I try to update drivers, UNO R3 is found but then I get a third party INF does not contain digital signature error. Doesn't give me a choice to install anyway, just finish to close the wizard.