I need some help!!

My system is:

MotherBoard - Chaintech 6AJM4/G100 , VIA694X+686B
CPU - iP3-Celeron 733Mhz
RAM - 2x128Mb SDRAM PC133

And the problem is that I can't overclock the CPU.
Tryed by hardware... didn't work. With any combination, the screen just remained blank and I had to reset the BIOS.
Tryed by BIOS... I could only go to 783Mhz, the rest of the combinations make the same result as explain just above.
My BIOS is on Optimized Defaults, but I've also tryed Safe Defaults.

What do I have to do to get some speed on this?

Thanks in advance,
Winged Dragon ][