As it says in the steps to get a perfect Clean Reinstall - Factory OEM Windows 7
you should use the drivers
which come with the installer and are quickly updated via optional Windows Updates. After several rounds of Updates any drivers still missing in Device Manager can be found on the Alienware Support Downloads webpage for your model. The drivers in the disk may be older than these. I would not change out any drivers given by the installer or optional Updates as Windows 7 is the authority on its drivers.
Did you check the Drivers disk to make sure you didn't miss the Log On theme? Also check the Alienware Downloads webpage for your model.