Okay, now we see that your hardware seems to confirm what your Minidumps have at least pointed to as my first post suggests. You have a nVidia chipset and you have an AMD cpu (by the way if that is an Athlon 64 3200+ Venice, well I have the same chip).
I do have a few questions:
1. To make sure I am reading you correctly, you did run a harddrive diagnostics and no errors? If you didn't run this diagnostic I suggest you do so.
2. Can you tell us your motherboard manufacture?
I am still of the opinion that the drivers for your chipset is the issue. Here is another step you might want to take:
A. Go to this link:
http://www.amd.com/us-en/
B. Find the Support Column on the first page and under this column click on Microprocessore Tech Docs.
C. Another page will load. Scroll down to AMD Athlon 64. Click on Updates, Drivers, Utilities.
D. Still another page will load. Scroll down to Machine Check Analysis Tool and read. You may want to download this.
To be honest I have never used this before and it would take someone with more knowledge than me to read the information. Nevertheless, I am sure someone here could. Your second minidump clearly called attention to hardware error and Machine Chech Architecture.
* I strongly suggest that you find the make and model of your motherboard and contact their tech support and tell them that you are experiencing the issues listed. Just cut and paste if need be and send it along.
* If this is a computer you bought as a whole and it is still under warrenty then by all means they are responsible to correct it.