The P965 chipset is only designed to support 1066FSB, however most boards will do 1333 with overclocking or a bios update to make the board auto overclock the chipset....
Please note that my P5W will NOT do 1333FSB(on dual it errors in prime after 45 minutes, on Quad it just freezes up solid...) even tho asus says it will....gonna have to try more voltage to see.....
From what i hear the P5B is supposed to be an OK clocker....
If you have the board then you have nothing to loose if you do not...go for a P35 based board as they are MADE for 1333.