My computer randomly started freezing every time I watch a video on divx in full screen or when I turn on visualizer on full screen for itunes and when I watch shows on windows media center in full screen. Just recently I tried to view a photo and it did the same thing froze when I was in windows image viewer. Now it starts freezing anytime I am over 30% in CPU Usage. I have used my Anti Virus programs and they found nothing, I restored my computer to an earlier date and that did nothing, I claned out my computer case and that did nothing, I updated my video drivers and that did nothing. I have a HP Windows Media Center Desktop Computer with Windows 7 Ultimate/ AMD Phenom 9500 Quad Core Processor/ 3.00 GB of RAM/ 32 Bit Operating System. If someone could please give me any idea on how to fix this or get rid of this problem that would be great.

ram usage is about 1.7gb.