I have an Asus M3A78-EM that shows a problem in Device Manager. It's listed under Other devices and says that it is an Ethernet Controller. I have no idea how to identify this device further so I can clear the asterisk.
More about :ethernet controller driver windows bit
Since this is a board is a bit older and you have installed a brand new OS on it, the first thing you should do obtain all the latest Win 7 32 bit compatible drivers from the ASUS website for this motherboard (namely and most importantly it appears like you need a LAN or Ethernet driver at least) and install them if you have not done this already. If you have and you are still having this issue, let us know.