urgent help: Can't install arduino Uno in vista

Hi guys,

I can't install my arduino uno in my laptop which runs on windows vista.

I have followed the steps as instructed here: http://arduino.cc/en/Guide/Windows#toc4
and I encountered a problem at the step where I have to look under Ports and "arduino UNO (comxx)" will be there. But I do not have that arduino UNO (comxx) under the ports...

Anyone can help? I need to install and use the UNO quite urgently.

Thanks.

Where did you buy your Arduino from?