Problem installing Uno Driver in Windows 7: "Access Denied"

Hi,

I'm having trouble installing the Arduino Uno Device Driver "Arduino Uno.inf". I first of all tried using the device wizard ("dpinst_amd64.exe") to install the driver but it continually comes back with the message "Windows can't verify the publisher of this driver software". I select the option "Install this driver software anyway" but it comes back with the same windows about a minute later. So I gave up on this method as it appears that the device driver doesn't have a valid digital signature eventhough I downloaded these drivers directly from the Arduino website.

The second method for installing the driver:-
When I connect the Arduino Uno board to my Laptop through the USB port, which is running Windows 7, it doesn't recognise the Uno device which is connected to my com port, so I manually tried installing the driver "Arduino Uno.inf" from Device Manager but I get the following message:- " Windows found driver software for your device but encountered a problem while attempting to install it" "Arduino Uno" "Access is denied".

I have done a number of things including disabling Windows Firewall aswell as switching off the anti-virus but to not avail.

Any help would be much appreciated.

Thanks,
Paul

im having the same problem too in windows 7.
on another windows 8 PC it is able to work just fine