If it is not the program it is likely the CPU cooler isn't making good thermal contact with the CPU or your cooler fan is not working. Since it just happened all of a sudden I guess we can rule out case airflow - unless one of your case fans has failed.
First thing I would check is fans. Then if that isn;t the problem. you will probably need to take of the CPU heatsink, remove all thermal paste, then apply new thermal paste and re-seat the heat sink. If you don't feel comfortable doing this, then take it to a local computer store.
BTW, filling in your hardware spec can aid in resolving hardware related issues.