video card issue (i think)

i got a nvidia geforce 6200 this past x-mas from sam's club (i know not the place i shoulda gotten it from but money was tight) and i installed it in my machine and have fully up to date drivers...well i started playing es4blivion in windowed mode and every once in a while the screen would go black but i still had sound. had to restart to get video back. so i turned off v-sync within game vid options, played in fullscreen and the issue stopped....well a few weeks later my computer would "hibernate" but the fans were still running in the tower but that was it.... the monitor came up with "check video card settings" which hadnt been changed...and this would happen even with the machine just sitting on the desktop...here's the dxdiag info on the device:

thnx in advance for your help

**edit** also nothing was in windows event viewer that would cause this