Many older online forums claim the MG43M stops at 4GB. The clarifies that with a BIOS update (version P01-A4 or later), the board supports 8GB using four 2GB DDR2-800 sticks. However, Windows 32-bit will still only see ~3.25GB.
Centrally located, surrounded by the LGA775 retention mechanism and the Intel G43 Northbridge (under a heatsink). acer mg43m motherboard manual new