Pc freezing up

I'm running win 7 Ult 64 bit. My pc has started freezing up when starting a large program or when stopping a game (large or small) I get a black screen, I hit esc
nothing happens. hit ctrl-alt-del nothing happens. I have to turn power off and restart.
Other than this problem everything else seems good. Thanks for any help!


Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Ultimate, Service Pack 1, 64 bit
Processor: AMD Sempron(tm) 140 Processor, AMD64 Family 16 Model 6 Stepping 2
Processor Count: 1
RAM: 2814 Mb
Graphics Card: NVIDIA GeForce 6150SE nForce 430, 256 Mb
Hard Drives: C: Total - 293968 MB, Free - 133837 MB; D: Total - 11142 MB, Free - 1587 MB; H: Total - 29 MB, Free - 16 MB;
Motherboard: PEGATRON CORPORATION, NARRA5
Antivirus: Norton 360 Premier Edition, Updated and Enabled