hmmm, a tough question you present young padawan....
I believe, and this is just me, 4 gigs of RAM is a little much...I mean, seriously.
I have 1.25 gigs with 512 on card (ATI X1600) and my pc eats SHIII for breakfast(sh4 runs okay, but a little shoppy here and there)....ENigma I believe only works with 32 bit...well stew my foot and call me brenda...i have the box....and it has wonderful advertising....
ummm...
perhaps your computer overpowers the game and it won't run because its TOO good? ive had that hapen before (had to pitch my copy of rainbow six...
)
sorry I cant be of much help, but it should be a start