I need some help with my Overclock ! I wanna Try and get this chip to 3.8 or even 4 GHz

Currently running a Q9450 470x7.5 Stable using these voltages

NB 1.37
FSB 1.33
CPU 1.31
PPL 1.51

GTL's on Auto

If I use the x8 Multiplier using the current voltages I get a Blue Screen.
Any Help would be greatly Appreciated