Cheers Smooth! It's an i7-4770, standard clocks and all, running 6 threads, above normal priority.
Why don't you run all threads/cores but in low priority? Windows can manage just fine the other jobs that way, and you can have the max hashrate too.
I even play Left 4 Dead 2 without stop mining. The hashrate drops from 850 h/s to 550 while playing but that's all, I have to do nothing else.