Installing Drivers for Arduino in Windows 8 / 7.
( I tried it for Uno r3, but i believe it will work for all Arduino Boards )
Plugin your Arduino Board
Go to Control Panel ---> System and Security ---> System ---> On the left pane Device Manger
Expand Other Devices.
Under Other Devices you will notice a icon with a small yellow error graphic. (Unplug all your other devices attached to any Serial Port)
Right Click on that device ---> Update Driver Software
Select Browse my computer for Driver Software
Click on Browse ---> Browse for the folder of Arduino Environment which you have downloaded from Arduino website. If not downloaded then http://arduino.cc/en/Main/Software
After Browsing mark include subfolder.
Click next ---> Your driver will be installed.
Collapse Other Devices ---> Expand Port ( its in device manager only under other devices )
You will see Arduino Written ---> Look for its COM PORT (close device manager)
Go to Arduino Environment ---> Tools ---> Serial Port ---> Select the COM PORT as mentioned in PORT in device manager. (If you are using any other Arduino Board instead of UNO then select the same in boards )
Upload your killer programmes and see them work . . .
I hope this helps. . .
Welcome