That mobo allows the use of either the 2 x 184 pin sockets or the 3 x 168-pin sockets, but not both.
I know for a 100% certain fact that the DDR capacity of that mobo is NOT 2GB RAM! I have a PC with that very board, and it will not accept 2 x 1GB modules. If you hunt hard enough, you will find that admission by Asus on their website.
It "should" therefore take up to 1.5GB DDR (1024 + 512 184 pin modules) - I'm running it with a single 1GB module, and I tried it with 1.256, but I thought it was unstable.
I've not tried it with the SDRAM modules, as they are very much slower.
I've just bought a replacement mobo that I can utilise the AGP graphics from this PC and the Athlon 64X2 from another PC where I upgraded the CPU.
To be honest, the single core PC is now very slow, even with Win XP, and I want to move on to WIN 7.
Upgrading the RAM on that PC is throwing good money after bad, IMHO.
SD