Depending on the age of your computer dictates what cables you need! If your PC is an older one and has a 9 pin serial port on the back you just need the standard etrex PC connection cable from Garmin.
If yor PC is a newer one - they don't have serial ports anymore - you will also need a USB to serial adapter.
As my PC is new I have to use a USB to serial adapter to connect my etrex H, and am happy to say all is working fine!!
Happy Hunting..