kathy32 0 Newbie Poster

I am upgrading a hp pavilion xh365 laptop, i am wondering if a pc133 rather then a pc100 will work and also, the max. memory this thing holds is 512mb i am wanting to know if i just put a 512mb memory in it if it will just override the factory 128mb in it? since the max. is 512mb it has 2 banks and there has to be something in each one or will i have to put 2 256mbs in it? i am trying to do this the cheapest possible and the pc133 is cheaper then the pc100 and the 1 512mb is cheaper then buying 2 256mbs.... i think i have to have matching sets in each bank though,,can someone shed some light on this for me,,,confused..