What are the system TEMPs ?
If temps are high....try Bob's suggestion by removing a case side panel and see how that affects system temps.
Are the video drivers up to date ?
Have you tested the RAM ...with something like 'memtest86+ ?
Part of the problem is when media player is playing in skin mode and the display is on the random visualization,then expand to full screen: the display freezes for .5 seconds then goes to normal. The other part is I cant play any game for more than 1 minute, it will flicker badly and soon after freeze/reset the OS! I even tryed games I was able to play fine a couple weeks ago,they all crash. I tryed all drivers from msi, nvidia, all all versions of those drivers. I did get one of the games to play for 10 minutes on the Lowest settings, but it eventually crashed too! This leads me to one conclusion that it is a hardware issue. I reseated the RAM, the graphics card,cleaned the system out and still no help. So something is faulty. Either its the mobo(msi k9n platinum), graphics card(msi 7900gtx), power supply(rosewill 600W).
Since the OS works flawlessly, the problem is exlusively the graphics, so am I wrong that it is the graphics card only?