Sys. req:
1.9 Ghz Intel Pen*tium or similar AMD
512mb RAM
Direct X 9.0c
128mb compatible video card & support for pixelshader 2.0
So a 6600 chipset nvidia card should be enough for the grafical parts. On the other hand, I think 512 megs of memory will not be good enough, or at least it will be really laggy. EU3 runs quite crappy on my other and older computer with that much of memory.