Go to:
Start -> Control panel -> Systems.
Go to the hardware tab and click Device Manager. Look for the device you want to update the driver for and double click it. Go to the driver tab and click on Update driver.
A screen will pop up like in the automatic install (The Windows Assistant). Select Install for a list or specific location this time and click Next. Uncheck Search removable media and check Include this location in search. Click the Browse button and go to the directory where you saved your new driver (you have to know where the file with the driver is located). If its on CD (s just search removable media and it will find it.
Click Next and it will attempt to install the driver. Once done click Next again and your new driver is install.
I recommend a System reboot for the device to work properly.