Go to device manager and right click on the device, and select install driver.
Click on "Browse my computer for driver software".
When you browse for the drivers, they are located in the Arduino IDE directory.
I installed the Arduino library on drive C: to make it easier.
I then looked for "C:\arduino-1.0.1\drivers" for the driver path.
Look to see where the main Arduino program installed, maybe in program files?
Here is the link on installation from the Arduino website:http://arduino.cc/en/Guide/Windows
That little black caterpillar you just stepped on will set you back a few bucks....