Toshiba Qosmio same problem as above.

Hey man,i saw your post and thought maybe you can help me.I have a Toshiba Qosmio F-25 AV205 laptop.Its worked fine until about a week ago when suddenly it would lock up during use for no reason.Now at time when i boot i will only get a blank screen and the Processor fan will kick into overdrive.Other times i get past Bio's to the windows login screen but then it will take forever to load or result in a Blue screen error which flashes to fast to see or lock up.I tryed replacing the hard drive,restoring to factory defaults using system restore and changing RAM but nothing helps so far.Im fearing now its the motherboard,processor or graphics card but the problem is how to determine which?the blank screen upon boot up 80% of the time leads me to think the processor or Graphics card.But then the random lock ups once in windows makes me think Mobo or processor.Any thoughts or suggestions would be appreciated