Could be a few things.
Your CPU might be heating up too quickly (maybe your LC isn't installed properly?). What CPU temperatures are you getting when you turn on your computer?
What is LC? And I cant seem to find the event viewer on my win7. Same problem... but suspect either network card because I keep getting a page fault in non paged area blue screen, but lately it has just been shutting off, not shutting down... OFF for no apparent reason. Any further help would be appreciated.