Ok I just tried to install 128 megabyte PC800 RDRAM modules into a Sony Vaio ---there were already 2 sticks of the 64 meg RDAM previously installed--am I missing something here? What could cause the RDRAm to not work with each other? I have four slots--previously there was a 64 stick and then the cimm, a 64 stick and then another cimm. I changed it to 2x128 and then 2x64 -- and the machine wouldnt boot. I heard that RDRAM can be bitchy about using sticks from diffferent manufacturers--is this possible? how about could it be a mismatch of ECC and non-ECC? I cant find any info on the old sticks to detremine if it is ECC or not. The new ones are non-ECC.