Put some better cooling and increase voltage to about 1.6 at first, than, if things get unstable you can increase a bit more. All this time monitor temps, above 55-60 under load isn't good. I don't know what mobo/RAM you have but it helps having one with a 865PE/875P chipset and PC3200 RAM.
Thermalright make some good stuff, the SLK-947U and SP-94 are both very good (the SP-94 is better), pair them with a strong 92mm fan and you're set.
You can, if you want, run the processor at a crazy voltage and get like a 70% OC, but that won't last too long ;].
Yea, though I walk through the valley of the shadow of death, I will fear no evil, for Thou art with me; Thy rod and Thy staff, they comfort me.