CPU low usage, with Matlab 2012a

Dear all, I am running a code in matlab 2012a. The CPU usage is very low (about 10%) with a PC of core i7 and 3.2 GHz and a 8 GB ram. How can I raise the CPU usage and speed up the calculation? The calculation time is about 80 hours with PC, while it takes about 8 hours with a system of core i2, 2GH and matlab 2007! What is wrong with it?? Please help me… Regards