pc trouble

[hammerhead]

any one know anything about pcs?
really could do with some advice even some remote assistance every now and again my pc comes up the blue screen of death ive gone into the physical memory part and done what i can to arrange the settings as some one has told me but it still does it from time to time and also its not letting me update my windows i am stumped ive ran a full scan defraged it dick cleaned it etc.
the pc itself ran on xp but was upgraded to win 7 for the last year ish if any one can help please please do i really need the pc up and running for work.

steve