Your current setup should be ok to run the game at low to mid settings, it also depends on your operating system, for example if you have Windows Vista you only have a GB of RAM available for the programs (approximately) which is a "recommended" for this game.
Your video card has 256 MB of dedicated RAM, so that should give you enough to run low-mid settings.
Your harddrive space is, of course, enough (game only needs 8GB max)
Your CPU can probably handle it, Demigod isn't a CPU intensive game, but you may expect a little bit slower loads/lag during intensive battle times.
Also, dual/quad CPUs do not "add up" in their working frequency, each core threads its own processes or part of them.
If problems do occur, I suggest getting friends that know their way around the computers and do the following:
1) Add an extra GB of RAM
2) Perhaps try and overclock the CPU to 2.2-2.4GHz, unless your PC is one of the big-brands (HP,Dell etc), then you can't OC them to full potential due to motherboards being locked.
Hopefully this helped you a bit.
