I guess you have, but just in case: have you checked you RAM modules for errors? A memory test could shed some light on this. If one of the modules is damaged you would get a blue screen whenever the system tries to use the damaged part of the memory. (And the more memory is used (simulations and stuff), the more likely this gets.)
I would do a disk check, since you installed the sims, you’ve been getting this. Seems to me like your computer may be using bad sectors as swap for ram. This will lead to errors.