Getting started with Arduino UNO
From MCS Wiki
Procedure
Download Arduino Software
http://arduino.cc/en/main/software
Create an folder Arduino e.g. C:\arduino-1.0.3
Copy the Arduino files into C:\arduino-1.0.3
The drivers can be found under C:\arduino-1.0.3\drivers (not the FTDI USB Drivers)
If the Arduino UNO was already connected then use following help http://arduino.cc/en/Guide/UnoDriversWindowsXP which is similar to Windows7 or Windows8 procedure.