NM: parity check

I purchased my Dell August 2008, I have a Dell xps1530 and it has vista on it. The only problem I have had with my laptop is that it gets hot so I picked up a fan that blows across it keeping it cool. About 2 weeks ago while I am in the middle of a game, watching a movie on Netfli, sending an email the screen turns blue and has the message hardware malfunction NMI: parity check/ memory error. I would have to force it to shutdown and it would start right up with no problems. Today when I went to restart my computer it doesn't start all the way. One of the time I tried to start it I pushed the media direct button and it started to work then I got this message .... c:\programfiles\dell\mediadirect\mdirect.exe is not a valid win 32 application..           I am trying to find a fix that will not take a lot of money since I don't have any.                                                                                                                                      

Thank you

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