My some what broken compaq evo n610c

ok when i start uo my labtop it loads then says unsafe shutdown and list choices safe mode safe mode with network safemode with command prompt start with last known config that worked and start normaly. heres where it gets wierd ive tried every option and it loads upto the windows xp service pack 2 btw and then quickly flashes a blue screen then restarts and i cant get it to stop its been going on for days every time i try same thing cant run system req i think never figured out how to.... but if any 1 at all can help plz do thank you.