GeForce 6200 AGP 256mb - Video Crash, Help Needed!

Hi! I searched all over the internet for a possible match for my problem, no luck, just partial matchs...

After some time playing a game or a 3D application in Full Screen mode the video hangs, only the video (after some seconds after the crash i'm able to interact with the computer but the image is still crashed).

One curious thing i noticed recently is the fact that if after the crash i close the application (ALT+F4, because im still "blind" ) and launch another application (that changes the display mode) the image come again to the desktop with a Direct X error, if using RivaTunner I reload the graphics driver everytihng is ok...

Theres my system:
Processor: AMD Sempron(tm) 3000+, MMX, 3DNow, ~2.0GHz
Memory: 1024MB RAM
Hard Drive: 80 GB
Video Card: NVIDIA GeForce FX 5200
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_gdr.050301-1519)

Im not sure about the motherboard, its a AsRock K7 something, I Think, but not sure.

Any help is appreciated, thank you.

Regards, Antonio Pinto