to decompress the files you need something like:
tar -zxpf speedtouchconf-2.0-beta1_12-Mar-2005.tar.gz
any errors probably mean a failed download .... ie. try again!
I have no idea about Wanadoo Broadband or Speedtouch 330 modems.
I have a dual usb/ethernet modem which I run as ethernet only
(and just to make that more complicated it's in half bridged mode