Video card issues

I have installed a nvidia geforce 6200 OC graphics card. I did disable my on board graphics controller. Also check in bios and it is on auto and not the on board graphics. When I play Sid Meier's Pirates game -it will play for a minute or two and then freeze. The computer shuts down after a bit and then automatically restarts. After start up a message I get is 'your computer has just recovered form a serious error. So I send info off the microsoft and it says that it is Dell on board graphics controller. It says to up date drivers etc. IT also says there is no solution at this time . I am running a demension 3000 -2 gig of ram -