It looks like a graphics card issue. All of your dump files are showing
nv4_disp.dll 3/21/2013
as the issue which I assume is part of the driver package for your Nvidia GeForce 6200. You can try doing a clean install of the latest version of the driver from here
http://www.nvidia.com/download/driverResults.aspx/57493/en-us
If that doesn't help you may consider either rolling back the driver to a previous version, or......
Update the system BIOS from the manufacturer's website.
Or on an older system such as yours you may need to consider updating / upgrading the Power Supply, replacing the card with another if either or both of those are a possible option.
And just to touch all the bases do a memory check ..