I've got my wii on my home-lan (lan-adapter on usb-port). What i would like is to see the wii/external HD of the Wii/sd-card of the Wii on my network (On my Windows pc)
You can do so with a FTP app, like FTPii or WiiXplorer. You will need to connect your PC and your Wii via FTP, so you will also need a FTP client for Windows.
I don't know if everything in your Wii's NAND will be shown (your sd card will be fully shown though).