blue screen

I have a problem with my xps450 desktop ,cpu 9400 2.66ghz

4 g memory,Nvidia ge force 9800gt, 32 bit. When I boot up and after a few minutes , I get

 the blue screen, stating beginning dumping of physical memory. I disconected external hard drive and printer

but still get the message every time i boot up, some times I can run for about 5 minutes before I get the blue screen

after I get the blue screen it changes to another screen giving me a choice to safe mode or  safe mode with internet

it will run in safe mode but as you know not with all the drivers. I am loss as what to do has anyone got any ideas what could be the problem ?

  Bob Moyer