overclocking problem with intel gma hd

[trolleras9]

when overclocking through bios,
increasing igpu frequency windows 7 wont boot at all
so i have to return value to stock, if someone knows the problem pls answer
help would be appreciated

 

[EarthDog]

Increase in smaller steps? What did you try to set it to initially?

What mobo and CPU?

A little more information would be helpful to help you out in the most efficient manner.

 

[trolleras9]

by stock value is set to auto , when pressing + goes to 1150 and then increases 100mhz at a time
cpu intel core i5 3470 3.2ghz not overclocked
motherboard asus p8h61-m lx r2.0
gpu on board intel gma hd 2500
windows 7 home premium 64bit
4gb ram and frequency set to auto, dont know why(should be 1600mhz) ddr3 of course
oh and an additional question whats the difference between igpu clock shader clock and core clock,?
thank you