I cant overclock plz help

[ShadiGhabboun]

hey guys
so my mother board is gigabyte intel 945gcm-s2l and my cpu is C2D E4600 (2.4) so i was looking through the internet and i found that i can over clock it to 3.0 GHZ so i followed the instructions and it was great i had it done and everything is ok but after about 2 weeks i found that it got back to 2.4GHZ so i tried to overclock it again but when i restart it just go back to 2.4 so can anyone help me plz
thnx alot

 

[ShadiGhabboun]

guys i dont know if this is important but i upgraded my rams from 2 gb (1*2) to 3 gb (1GB+2GB) before about a week