Hi, I am trying to overclock my system.

CPU: Intel Core 2 Quad Q6600
Ram: 3x 1 GB DDR2
Motherboard: Gigabyte P35-DS3L
Graphic Card: Nvidia GeForce 8800 GT

I tried going into Bios to change the settings and every time I change the settings, it reverts back to 2.40 ghz. I've only ever attempted to overclock up to 2.8x ghz. After saving and exiting bios, the computer turns off, I can hear the fans going as it turns on and then it turns off again (screen blank). Then it attempts a boot up again and does the same thing before finally loading up the operating system. When I check on my computer, it shows the system as 2.40 ghz. I've only ever gotten it to show 2.8x ghz once and after I reboot the computer, it changes back. What am I doing wrong?

Please help, thank you.