Hi dollkey,
I had a look on that website at my specs. My processor is slower than yours and my graphics chipset is the 3 series, however I have 3GB of RAM and it results in a pass. So it looks like, if you got extra RAM, then you would be able to pay.
I play full-screen, all lowest settings and at 800x600. Play is smooth, though not as pretty to look at as it would be if I had a graphics card.
In the meantime, are you patched up to date? The latest patch solved my crashing problem (my screen went black and the laptop turned itself off) that was caused by placing a building that brought the security level up to over six. Your current problem sounds similar to what was happening pre-patch.
I've still crashed, on occasion and have no idea why as, after a reboot, I've been able to continue. I've just been making sure to save regularly and exit the game at least every hour. It's been fine for the last four hours (oops) of game play.
Good luck.