4W4K3 is right one with that: the PC133 chips will downclock to PC100 however you should be ok in either case -- it's not often that there is a memory conflict however considering how closely PC133 and PC100 are relatedis it ok to use 2 sticks pc133mhz with a pc100mhz in same system
I wouldnt go so far as to say "trouble" ... too doomy and gloomygo for same kind or your in for some trouble.