Stephen is right- your computer isn’t powerful enough, which is why you’re getting the stuttering & freezing. That processor might be fine enough for lower-quality HD footage (ie- footage below 24 mb/s), but high-quality 1080 footage is taxing your hardware.
Sorry to say, but it’s time to upgrade to an Intel Ivy Bridge processor and Z77 chipset motherboard. With today’s memory prices, i’d get 16gb of RAM minimum. Plus, you never stated what type of drive(s) your video footage is residing on.
Dave