The specs: http://www.e4allupgraders.info/dir1/motherboards/socketa/au31.shtml
According to those specs it should have worked. Provided you got the right ram and no other problem(ESD/static damage) it should have been a drop-in upgrade. You can return the bios to defaults, use the CMOS clearing pins for that. Install the ram and see if it boots. If not, then it maybe time to return the ram or test them elsewhere, if possible. Use http://www.crucial.com for assured proper ram buying or check out as well. There's the outside chance if you hadn't done it, a "bios update" maybe needed as a fix, but be sure to know what the bios update does. If that bios supports such, see if upping the ram voltage a tad for stability.
I am trying to upgrade the RAM in my eMachines computer with a FIC AU31 K7M-NF18G motherboard. The specs that I can find on this mobo say that I should be able to put up to 2GB of RAM in it. I purchased two 1GB 184-Pin Unbuffered DIMM 128x64 DDR PC3200 modules (which should work in this mobo). When I take out the current RAM and install these two cards the computer will not boot up. I have tried to add just one card at a time to see if one of the cards was bad but neither of them will let the computer boot up. (Yes, I installed them one at a time in the same slot the old card came out of). Am I missing something? I have some basic computer knowledge and it should be a simple plug and play swap. Any ideas?