WARNING: Always use TFTP to flash Belkin routers if at all possible! Upgrading dd-wrt from the web interface can lead to a bricked (nonfunctional) unit! NOTE:During configuration or flashing a device, the only that should be hooked to the device is the computer and power.
In Windows XP, Click Start Button - All Programs - Accessories -
Communication - HyperTerminal
Enter a name for the connection, Click ok
Choose com port you adapter is plugged into, Click ok
Bits per second = 115200
Data Bits = 8
Parity = none
Stop bits = 1
Flow control = none
Click File - Save As, and select a place to save it to so you
don't have to enter the settings again.
After installing putty, run it
Serial line = The COM port your using for serial (ie. COM3)
Speed = 115200
Click on Serial under Connection
Serial line to connect to = same as above (Serial line)
Speed (baud) = 115200
Data bits = 8
Stop bits = 1
Parity = None
Flow control = None
Enter a name for your connection under saved sessions
The USB port is where you can connect an external USB hard drive or flash drive. Which can do a multitude of things. You can use in as a NAS, storage for a FTP server, use Optware to run external programs like torrent software, samba for sharing files to your network, share a USB printer with your network... The list of possibilities is long, it just takes a little research.
ProFTPd is included in most the newer builds of dd-wrt. Check the features chart to be sure.
A ftp server, file sharing, and a media sever is included in TomatoUSB if your device is compatable.