Im somewhat smart overclocker so one thing im still fuzzy on,,Voltage.

I can get my 2.4 northwood Celeron to 3.0Ghz FSB@125mhz pc-2100 Kingston 256X2 with thermalTake coolers running at 333mhz.
Max CPU Temp running prime95 is 42 degrees C.
with mobo default voltage settings, can i up them a little to gain performance or just more heat??

First, read the sticky on the top of this forum.

http://www.techspot.com/vb/showthread.php?s=&threadid=10514

Secondly, when overclocking, you can up the voltage if you find the system becomes less stable at higher frequencies. It may not make it perfect, but better. Adding more voltage, however, give a better chance of smoking something in your system. I wouldn't recommend anything more than +0.2 above the manufacturer's recommendation.
Good luck,

Bug