You can either use a crossover cable or a straight-through (normal ethernet cable), ftp client (FlashFXP, Cute, WSFTP & others) to connect from the ethernet port on xbox to your ethernet card or port on the PC or hub ( or cable modem/router, switch. Next you will need to setup your xbox with a IP address (I setup using static). Start up Client FTP and insert IP address of xbox, insert username and password (usually xbox & xbox or x3 & x3 depending on whether you are going through dashboard or bios. Hope this helps.
you cant use a straight ethernet cable from your xbox to your computer, it has to be through a router or else use a crossover cable. by the way make sure you are putting in your current ip into the ftp client