Hi
Is it profitable to mine with my old computer quad core cpu ?if yes how much per day?
Short answer:
Yes and 240ish (some days more, other days less)
Slightly longer answer:
Depends on the processor, OS and if you mining as part of the cluster or a pool.
Long answer:
I'm still researching as I'm playing with various setups such as virtual machines, laptops etc but one thing I have worked out is that mining in Linux gives a better h/s than windows, even if you run Linux in a virtual machine on a windows box...