so i just got this lenovo desktop pc with windows 7 on it. When i first got it it was all fine and dandy but now it has begun restarting it self out of no where... it actually has restarted 4 times in the time of me tryin to post this i have no clue whats wrong the screen just freezes then goes black and hesistates for a minute then fires back up...to me it seems it does it more frequently when im doing more stuff on my pc like browsing web downloads etc... can some one please help me...