The analysis report of your minidumps are crashed with bugcheck 7F and nt status code 8 (ie double fault) at nVidia Display card driver. Usually it is symptom of stack overflow or hardware error.
Maybe your windows has multiple culprit. The first culprit is the hardware error at your nVidia Display card. I resolved a similar problem at another forum but this forum requires registration. The problem owner try different version of nVidia Display card and it still crashed with symptom Bugcheck code 7F and nt status code 8. Finally he replaced the video card by the old ATI display card and the problem was resolved. http://www.experts-exchange.com/Operating_Systems/WinXP/Q_21568581.html
The second culprit is faulty ram as one of your minidump is inaccessible and this is symptom of bad ram.
