No, you can't. You need a faster dual core, or overclock that one to 3 Ghz or 3.2 Ghz, and you also need a GTX460 to play Crysis Warhead on Max Settings (no AA though). And if you want to play Crysis on Max settings (no AA), you need to overclock the GTX460 a little.
As to just cause 2, I'm not sure, but probably not either.
My bet is you can try a combination of High or Medium Settings and lower the resolution to 1280x720, for example.