I think mining with a CPU is not an effective form. I've also tried to exploit some altcoin with the CPU, but it's not profitable for me because the performance is not high. In my opinion, you can use GPU or some professional exploiting machine will bring more efficiency.
What if you have an older computer that has already paid off its value with its work, but is it still strong enough to be able to dig up some crypto currencies? Will you still use it for ordinary surfing and CPU mining or will you throw it off? Btw. soon come new projects for CPU mining such as JSEcoin and Nimiq.
It's not effective. You will get CENTS.