The mbrd site is referring to a 266FSB version of the XP2600 ,so your 333FSB version is no good ,unless you fancy selecting a higher multiplier so that it runs at the correct MHz.
Thats assuming your mbrd can even do that.
AFAIK the XP2600 is the only CPU available in both 266 & 333 FSB ,most seem to be the 333 version