I don't think the hardware supports this with the A43. The 101 supports some USB ethernet adapters (smaller gen8 devices don't have enough power) and on angstrom or other unofficial firmware you could probably write your own /etc/network/interfaces files and set up ethernet over USB. I suggest you visit http://forum.xda-developers.com/archos- ... evelopment
and read about the various alternative firmwares for the A43 and maybe you can ask people there if any of them allow ethernet over USB on the A43, but I doubt you'll get the answer you'd like. You definitely can't do this in Archos firmware for A43.
If you want to access wired networks you can get a small, cheap wireless "Nano Router" such as the TP-Link TL-WR702N. You would attach this to a wired router or ADSL or Cable modem and make the network available wirelessly so you can connect with your A43.